I first created this list in early 2010 when I was using my Android phone to keep up on books while waiting for my nook to arrive from Barnes & Noble. Since then, it has grown and evolved. I don't read primarily on an Android device anymore, so if anyone finds something that has changed, is inaccurate, or a great addition to the list, feel free to comment here or send me a PM. I'll make sure to give credit and karma when possible.

It's definitely worth noting that =X= has most of this information in the mobileread wiki at this location. That's http://wiki.mobileread.com/wiki/EBook_software#Android just in case. Check it out. It's worth it!


The Big Booksellers


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Google Play Books
Cost: Free
Formats supported: (cloud), ePub, PDF
Online catalogs: Google Play

Notes: Google has introduced book purchases into their update of the old Android Market, making it easy to buy apps, books, and music. Books are stored in the cloud, but may be downloaded as ePub or PDF files.


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Kindle
Cost: Free
Formats supported: azw, mobi, topaz
Online catalogs: Amazon

Notes: Most popular eBook application in the market at this time. The best feature for those already using Amazon's Kindle is that the Android app "knows" where you stop reading. If you read a bit on your Kindle at home, you can pick up where you left off on your smartphone on the commute to work. When you pick up your Kindle at home, you guessed it. It syncs. Even better, for those who have rooted their nook color devices, it's like having Kindle and nook in one unit.


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Nook for Android by B&N
Cost: Free
Formats supported: ePub, prc
Online catalogs: Barnes & Noble

Notes: If you own a nook, this is the mothership. It has a refined interface, not quite up there with Aldiko, but definitely a good experience. Unfortunately, it weighs in at a whopping 17MB installed, and doesn't even integrate the B&N store into the app, sending eBook purchasers to the website instead. For Android users without apps2sd (via hacks or froyo) it's not worth it yet, but shows promise.


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Sony Reader
Cost: Free
Formats supported: ePub, pdf
Online catalogs: Sony

Notes: Sony's long-expected app is now out for Android, but only supports 2.2 (froyo) and later--pretty odd considering Sony-Ericsson phones don't run this version yet. The app does for Sony Readers what the Kindle and nook apps do for their respective readers in terms of functionality, offering download of already-purchased books, text highlighting, etc. One quibble is that it links to the Android browser to actually purchase material.


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Kobo
Cost: Free
Formats supported: ePub, prc
Online catalogs: Kobo (formerly Shortcovers)



General Purpose Readers


Book Place New
Cost: Free
Formats supported: ???
Online catalogs: Proprietary

Notes: An interactive reader that makes reading eBooks a multimedia experience. Optimized for tablets, this reader includes color, highlighting, text-to-speech, and a rich, graphical interface.


Mantano Reader
Cost: Free trial, with $7.49 full version
Formats supported: pdf, epub
Online catalogs: Google Books and other online catalogs

Notes: Supports Adobe DRM and password-protected files. Allows note-taking, text-to-speech, dictionary support, font customization, full range of filters for book searches. It seems to be the kitchen sink of ebook readers for Android.


Duokan Reader
Cost: Free
Formats supported: txt, ePub
Online catalogs: Available but unknown

Notes: Seems to be a good, general purpose reader. New to the market. The developer's website is in Chinese, but the app's description is in broken English, so I assume it supports most languages.


blio Reader
Cost: Free
Formats supported: XPS, ePub
Online catalogs: proprietary, with ability to sideload other content (no DRM)

Notes: Large (12MB) download. Multiple bookmarks. Phrase highlighting with lookup. Text-to-speech (TTS) with word highlighting as it reads (may be useful for literacy work). Can add notes (not just text) for serious study. Supports interactive books.


Go Reader
Cost: $4.99
Formats supported: pdf
Online catalogs: None

Notes: This is a full-featured PDF reader for Android. It integrates with gmail, dropbox, evernote, etc., and allows annotations and comments.


Aldiko Book Reader
Cost: Free with $2.99 "premium" edition available
Formats supported: ePub (including Adobe DRM)
Online catalogs: feedbooks, O'Reilly, All Romance, Smashwords

Notes: Sports the best interface of all readers for Android, using a cover browser on wooden library shelves. Has multiple methods of turning pages and a great night mode. It allows grouping of books into collections and has dictionary support. I don't think there are any differences in functionality between the free and premium versions. Instead, the premium version is more a "donationware" idea. The only cons I've found is it's impossible to click on links in the text to footnotes and it requires its books to be stored in a specific spot on the SD card, making book sharing or comparing among apps a pain.


Moon+ Reader
Cost: Free with $4.82 "pro" version
Formats supported: txt, html, epub, fb2, umd, zip, and OPDS
Online catalogs: Multiple sites

Notes: Has note-taking and highlighting features, along with online (Google, Wikipedia) and offline (ColorDict, Fora) dictionary support. It also has auto-scroll and online translation (again, Google). The paid version includes TTS (text-to-speech) capabilities.


Bluefire Reader
Cost: Free
Formats supported: ePub (with DRM) and PDF
Online catalogs: Multiple sites

Notes: Claims to handle about every ePub you can throw at it as well as PDF files. It supports Adobe DRM for ePub which allows books purchased or downloaded from multiple online sites to be read. One quibble is that pressing the "back" button loops from current book to the library and back.


iSilo Reader
Cost: $15.99 (Says currently $4 off, but that's off the latest increase of $6)
Formats supported: iSilo, pdb, txt
Online catalogs: Unknown

Notes: iSilo is a large, proprietary format made popular in the days of Palm devices. Clients are available for a wide variety of devices, making at least older books widely available. It's an old format, but has its die-hard fans, as evidenced by the hefty pricetag. iSilo, as a format, is hard to convert *from* but easy to convert *to*. This app comes with the CIA World Factbook free.


FB Reader
Cost: Free
Formats supported: ePub, oeb, fb2(.zip), mobi
Online catalogs: Just about any OPDS catalog

Notes: This is one of the best dedicated reader apps for Android. It has multiple page-turn options, a great night mode, and the ability to click links in the text for footnotes. It also allows you to store books where you like on your sd card. It has expanded its support for online catalogs recently to support any OPDS compatible catalog. If you browse to feedbooks.mobi and click on an ePub link, it will automatically download and import into FBReader. As an added bonus, there is a separate plugin you can download from the Market, giving FBreader Text-to-speech (TTS) support.


Cool Reader
Cost: Free, but donations accepted
Formats supported: epub, fb2, txt, rtf, html, chm, tcr
Online catalogs: Unknown

Notes: Cool Reader seems to be the biggest challenger so far for the longstanding kings of Android eBook readers. It's features include:
View as paper book pages or scroll
One or two pages in landscape mode
Internal file browser to open books
Configurable font face, size, style, interline space, text color, background (solid color, tiled or stretched image)
External fonts, background images, CSS styles
Book coverpages in file browser
Supports install on SD (Android 2.2+)
Customizable tap zone actions
Customizable key actions (including volume keys)
Can lock sensor screen and trackball
Can set custom display backlight brightness


LDS Reveal Reader
Cost: Free
Formats supported: ybk, oeb
Online catalogs: YanceyWare, Gutenberg, Mormon/Bible downloads.


Android chm Reader
Cost: Free
Formats supported: chm
Online catalogs: None.

Notes: This is a free, single-format version of the paid HYreader, which supports chm, txt, umd, and html files.


Palm Book Reader
Cost: Free
Formats supported: txt, pdb (no eReader or iSilo)
Online catalogs: None


txtr ebooks
Cost: Free
Formats supported: ePub (with DRM), PDF
Online catalogs: txtr.com


Android Txt EBook Reader
Cost: Free
Formats supported: txt
Online catalogs: None.

Notes: This is a free, single-format version of the paid HYreader, which supports chm, txt, umd, and html files.


Ebook Reader
Cost: Free
Formats supported: prc, epub, oeb, fb2/zip
Online catalogs: gutenberg, manybooks, feedbooks, booksinmyphone, freecomputerbooks, freetechbooks, and onlinecomputerbooks.

Notes: Based on FBreader.


Wordoholic Reader
Cost: Free
Formats supported: ePub, fb2, txt
Online catalogs: feedbooks


Captionary eBook Viewer
Cost: Free
Formats supported: epub, txt, zip
Online catalogs: None.


Ebook Reader
Cost: Free
Formats supported: S4BB
Online catalogs: S4BB

Notes: I have no clue what "S4BB" books are, and I try to shy away from proprietary formats, even if popular.


Speak Text Easy
Cost: $1.45
Formats supported: txt, pdf, epub
Online catalogs: feedbooks

Notes: Supports text-to-speech (TTS) in books. It claims to detect the language automatically. One reviewer claimed it to be better than Moon+ in this regard.


Wattpad
Cost: Free
Formats supported: Unknown
Online catalogs: Wattpad

Notes: Its slogan is "The YouTube for eBooks!" Has a teleprompter-like autoscroll mode. Also happens to be cross-platform. Downloads happen by obtaining a "wattcode" for a particular book from the Wattpad mobile site. Entering the code in the reader will download the book.


iReader
Cost: Free
Formats supported: txt, html, chm, umd, pdb, (mobi/ereader), and image files
Online catalogs: Unknown


GoSpoken Bookstore & eReader
Cost: Free
Formats supported: Unknown
Online catalogs: GoSpoken

Notes: This seems to be a UK-based bookstore offering an easy way to buy and read books on Android devices. Their app is cross-platform, allowing sync on up to five devices.


Inktera eBook Store
Cost: Free
Formats supported: Unknown
Online catalogs: Inktera

Notes: Yet another contender in the broadening world of store/reader combos.


OverDrive Media Console
Cost: Free
Formats supported: epub (ade) and wma audiobooks
Online catalogs: Overdrive at libraries around the US.

Notes: This is the software supported by most public lending libraries in the United States. It allows downloading of DRM-protected eBooks and audiobooks from your library.


Nightbook
Cost: Free with $1.50 premium version
Formats supported: txt
Online catalogs: Unknown


MultiReader
Cost: $4.86
Formats supported: pdf, ePub, txt, doc, rtf, ppt
Online catalogs: Gutenberg

Notes: Uses the text-to-speech (TTS) functionalities of the Android device to speak the text of the eBook. Works with multiple languages as well as several different voice services. In other words, it's not limited to just the Android speech synthesis system.

ezPDF Reader
Cost: Free with $0.99 "pro" version
Formats supported: pdf
Online catalogs: n/a

Notes: Seems to be an impressive PDF reader allowing the user to make annotations in multiple styles. It also supports text-to-speech (TTS) to have PDFs read to you.


eReader (Not in Android Market)
Cost: Free
Formats supported: pdb
Online catalogs: eReader.com, Fictionwise

Notes: bookmarks, highlights, notes, dictionary lookup when a compatible dictionary is installed. Owned by Barnes & Noble.


Readers for non-Latin Script

Check out Laputa Reader, Best Reader, Wisbook, and the below for a wide selection of readers supporting Asian scripts in horizontal and vertical modes. Searching for the popular formats, aozora bunko and chm, will also yield many results.


KingReader
Cost: Free
Formats supported: txt, umd, chm, html, jpg, png, bmp
Online catalogs: None


SnowLamp reader
Cost: Free
Formats supported: ePUB
Online catalogs: Unknown

Notes: Korean


Cbook
Cost: Free
Formats supported: pdb (big5 Chinese encoded)
Online catalogs: www.haodoo.net

Notes: Strictly a Chinese reader with vertical text layout.


Others to see not mentioned above include epubreader, starbooks, and PalmBookReader.


Comic viewers


ComicRack
Cost: Free with $6.89 paid version that eliminates adverts and allows wireless sync.
Formats supported: CBZ, CBR (natively), CB7, CBT, PDF, DJVU and WebComics (when sync'd with Desktop version)
Online catalogs: any WebDAV server.

Notes: Optimized for phones and tablets. Single and double page viewing. Auto scrolling. Right left to right reading mode for mangas. Color adjustments. Automatic page cropping for small devices. Full library management with lists and searching. Management of reading states (unread, completed etc.) and bookmarks. USB and Wifi synchronization with ComicRack for Windows.


Droid Comic Viewer
Cost: Free
Formats supported: zip/cbz, rar/cbr, acv, jpeg, png, bmp, folders
Online catalogs:


Perfect Viewer
Cost: Free
Formats supported: zip/cbz, rar/cbr, 7z/cb7, jpeg, png, bmp, gif
Online catalogs:


Androbook Viewer
Cost: Free
Formats supported: zipped jpg (cbz)
Online catalogs: androbook.net


ComicBricks - beta
Cost: Free
Formats supported: jpg, png
Online catalogs: Unknown.


jjComics Viewer
Cost: Free
Formats supported: zip, cbz, rar, cbr, jpg, gif, png, bmp
Online catalogs: Unknown.


Comic Reader Mobi
Cost: $14.99
Formats supported: zip, cbz, rar, cbr
Online catalogs: any WebDAV server.

Notes: Newcomer to the Market. Its most interesting feature is "Smart Lens" which allows you to tap on a text block in the comic, creating a popup of the enlarged text. It also has animated page turns, remembers where you left off, and many options to fit pages correctly on the Android screen.


ComiCat
Cost: Free
Formats supported: zip, cbz, rar, cbr
Online catalogs: Unknown

Notes: Notable feature: splits two-page scans into two separate views.


eBook Tools

Calibre Library
Cost: Free
Formats supported: the kitchen sink
Online catalogs: It is one!

Notes: If you use eBooks and don't know about Calibre, you've been living under a rock. Calibre, designed by MobileRead.com's own Kovid Goyal, is the swiss army knife of eBook tools. Originally designed for Sony's PRS-500, it has grown over the last five years to support most popular devices as well as a few less popoular ones. It allows for conversion between many formats, reading books on a computer, downloading periodicals...periodically, and acts as a server so that you can download your saved eBooks wirelessly from your computer to your devices as easily as you would from your device manufacturer's store. This app for Android is the client for that server feature.


eBook Optimizer
Cost: Free
Formats supported: ePUB
Online catalogs: N/A

Notes: Not a reader app, but claims to optimize ePUB files, making them 5-15% smaller for smartphone storage.


Bookfm Reader
Cost: Free
Formats supported: claims any, but client reads ePub
Online catalogs: none

Notes: You upload your ebook in most formats to www.bookfm.com. The website does the conversion to ePub and syncs with the phone client.


Free Library Books to Kindle New
Cost: Free
Formats supported: azw, mobi, topaz
Online catalogs: Overdrive catalogs from public libraries

Notes: Get free Kindle e-books (for the Kindle app) if you have a library card. In beta currently and only supports the metro areas of New York, Los Angeles, and Chicago.
Thanks, great resource!

I like FBReader myself.
Thanks!

Anybody know if any of those support Autoscroll?

Just 'cause my N1 is a touchscreen doesn't mean I want to be constantly tapping the screen to change pages!
I haven't seen any that support this feature. I haven't tried them all and don't know if I could for full reviews. The only "readers" I've seen with autoscroll are some news feed readers.

By the way, if you use any of the above, unreviewed clients, please feel free to post a review and I'll update the original post.
On the face of it there seems to be a lot of choice around for epub reader software for Android until you realise most / all of the above are unable to read Adobe DRM epub which is nominally still the standard.

Not a deal breaker for many on mobileread who prefer to strip the DRM but sometimes I do not have the time or can be bothered to strip the DRM and would happily just want to read a DRM epub on my Android phone.

So I suggest an update on the above list to clearly state which software can read what type of DRM epub (if any) would be useful.

It really surprises me that Adobe or A.N. Other big player who has adopted Adobe DRM epub e.g. Sony haven't put some resources into developing a software reader for Adobe DRM for use on Android / Windows / iphone. It is Amazon's strategy that I thought played well to the galleries. Being able to synchronize between your phone and dedicated ereader is functionality I want and I would guess is popular?
Looks like Kindle for Android is coming this summer.

http://www.engadget.com/2010/05/18/kindle-for-android-coming-this-summer/
I know, perfect timing on my part. I just posted the same news on a different thread as well.

As I said in my post above, I am interested in Adobe DRM epub, where are the DRM software readers for that! If Amazon can do it for Kindle.......
Repeat
I upgraded to an Android phone (HTC Desire) at the weekend. Wonderful gadget; so much faster than the Windows Mobile phone I had before.
I'll be buying iReader today, mainly because it covers Mobipocket DRM. While there is a free version, it's a much earlier version.
I have seen a few people wonder why sony haven't got an app on other hardware and the answer is pretty obvious, they are in the hardware business and what little interest they have in their bookstore is in how it helps hardware sales, in countries outside north america they didn't even bother with their own store and are just partnered up with local retailers e.g. waterstones in the uk.

Adobe on the other hand not being more proactive does seem very odd since the combination of adobe drm and epub was basically the standard outside north america with all ebook sellers with kindle being almost nowhere, but all that lead will vanish with the fragmentation of epub support due to ibooks and b&n using other drm and amazon getting a kindle app on every devicetype in existence.