eBook reader. Supports epub (non-DRM), fb2, doc, txt, rtf, html, chm, tcr, pdb, prc, mobi (non-DRM), pml formats. 

Pages or scroll view. Page flipping animation.
Table of contents, bookmarks, text search. 
Bookmarks on text fragments (comments or corrections) - useful for proof reading.
Export of bookmarks to text file.
Built-in file browser, quick recent books access. 
Online catalogs (OPDS) support.
LitRes online book store support.
Text to Speech (TTS) support.
Hyphenation dictionaries; 
Most complete FB2 format support: styles, tables, footnotes. 
Additional fonts support (place .ttf to /sdcard/fonts/)
Support for Chinese, Japanese, Korean languages; autodetection of TXT file encoding (GBK, Shift_JIS, BIG5, EUC_KR).
Day and night profiles (two sets of colors, background, backlight levels). 
Brightness adjustments by flick on left edge of screen.
Background texture (stretched or tiled) or solid color.
Paperbook-like page turning animation or "sliding page" animation.
Dictionary support (ColorDict, GoldenDict, Fora Dictionary, Aard Dictionary).
Customizable tap zone and key actions.
Autoscroll (automatic page flipping) - start using menu/goto/autoscroll or assign action Autoscroll on key or tap zone; Change speed using volume keys or bottom-right and bottom-left tap zones; stop - tap any other tap zone or key.
Can read books from zip archives.
Automatic reformatting of .txt files (autodetect headings etc.)
Styles can be customised in wide range using external CSS.
Select text using double tap (optional).

Place additional textures to /sdcard/.cr3/textures/ -- to be used as tiled page backgrounds.
Place additional textures to /sdcard/.cr3/backgrounds/ -- to be used as stretched page backgrounds.
(/cr3/ directory can also be used instead of /.cr3/, and internal SD or internal storage instead of /sdcard/)

CoolReader requires following permissions:
WAKE_LOCK - to control screen backlight
WRITE_EXTERNAL_STORAGE - to access SD card
INTERNET - to use online catalogs

CoolReader is free, open source (GPL), multiplatform project.
Project homepage on SourceForge is http://sourceforge.net/projects/crengine/
To donate this project, you can buy Cool Reader Gold ($10), Silver ($3) or Bronze ($1) Donation package from Market

In case of issues after update (e.g. crashes while reading) try to remove directory SD/.cr3/cache and book database files SD/.cr3/*.sqlite

Windows version can be downloaded here:
http://sourceforge.net/projects/crengine/files/CoolReader3/cr3-newui-opengl/cr3-win32-qt-opengl-3.3.48.zip/download

As well, consider using "Cool Reader GL" - cross-platform Cool Reader version with UI rewritten in C++, with hardware acceleration based on OpenGL. Optimized for new devices with big high resolution screens. Both versions can be installed together.

Project homepage: https://github.com/buggins/coolreader

Reading books in epub, fb2, txt, doc, rtf, html, chm, tcr, pdb, pml formats.