Main book formats: ePub (ePub3 is partially supported), Kindle (mobipocket), fb2(.zip).Other supported formats: RTF, doc (MS Word), html, plain text.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 synchronisation of your library and/or reading positions with FBReader book network (https://books.fbreader.org/), a Google Drive™ based cloud service. Synchronisation is disabled by default, go to preferences dialog to enable it and configure parameter.
FBReader is fast, highly customizable. Can use external TrueType/OpenType fonts and custom backgrounds. Screen brightness can be changed during reading (slide finger up/down along the left screen edge). Supports different day/night color schemes.
Supports YotaPhone Always-On Display functionality (can display text on both LCD and eInk screens).
Includes a browser/downloader for network ebook catalogs/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 put them into /sdcard/Books catalog on your device.
FBReader is integrated with external dictionaries. Supports ColorDict, all Slovoed dictionaries (by Paragon Software), Fora Dictionary, FreeDictionary.org, LEO dictionary.
Localized for 29 languages. Includes hyphenation patterns for 24 languages. Open-source (GPL).