Recently, I found a good Android book reader that's specifically made for language learning: Linga. It supports epub, mobi, pdf and fb2 files, comes with built-in dictionary, sentence translator, conjugation tables, SRS-based word-learning and a little library of free ebooks. Six languages are now supported: English, German, French, Russian, Spanish and Italian (not Hungarian as one might conclude from the flag on the web page
). Initially, I used to read books in foreign languages in standard book readers (Pocketbook, ReadEra, CoolReader among my favorite ones). Then I tried Steve Kaufmann's LingQ. A very good app, but not suitable for long texts. Linga was much better. Not without some imperfections, but it's a full-fledged book reader with some quite important additions.