FBReader

Popular e-book reader for multiple platforms comes to iOS.

Major e-book formats are ePub (including main features of ePub3), unencrypted Kindle azw3 (a.k.a. mobipocket) and fb2(.zip).
Other supported formats: RTF, doc (MS Word), HTML, plain text.

FBReader can synchronise your library, reading positions, bookmarks, etc. with the FBReader book network (https://books.fbreader.org/), a Google Drive™ based cloud service.

Alternatively, you can download books in the browser and open them using FBReader.​

Rich set of options allows you to configure reading parameters and app behaviour for your preference.

The free version of FBReader has few limitations. You cannot store more than ten books in the library. Built-in online translation feature is disabled. You can upgrade FBReader to the full version to unlock all the features.