FBReader is a free ebook reader.

Main ebook formats: ePub (including main features of ePub3) Kindle azw3 (mobipocket) fb2(.zip).
Other supported formats: RTF doc (MS Word) html plain text.

Formats supported via free plugins: PDF (https://www.google.com/url?q=https://play.google.com/store/apps/details?id=org.geometerplus.fbreader.plugin.pdf) DjVu (https://www.google.com/url?q=https://play.google.com/store/apps/details?id=org.geometerplus.fbreader.plugin.djvu)

FBReader supports synchronization of your library and/or reading positions with the FBReader book network (https://books.fbreader.org/) a Google Drive™ based cloud service. Synchronization is disabled by default; to enable and configure it use the preferences dialog.

FBReader is fast and highly customizable - it can use external TrueType/OpenType fonts and custom backgrounds the screen brightness can be adjusted while reading (slide finger up/down along the left screen edge) and different day/night color schemes can be selected.

This reader also includes a browser/downloader to access different network ebook catalogs and stores. Several popular English French Russian Chinese and Polish libraries are included. Custom OPDS catalogs are supported too.

Alternatively you can download books manually and save them on your device in /sdcard/Books.

FBReader is integrated with external dictionaries including Dictan (https://www.google.com/url?q=https://play.google.com/store/apps/details?id=info.softex.dictan) ColorDict Fora Dictionary FreeDictionary.org and LEO dictionary.

In addition this reader is localized for 34 languages and includes hyphenation patterns for 24 languages.