Gitden Reader!

Calibre is a free and open source e-book library management application made by users, for users. Many languages, designed around the concept of the logical book, i.e., a single entry in your library that may correspond to actual e-book files in several formats.

FBReader is an e-book reader for various platforms.

Innovative book reader with powerful controls & full functions:

Aldiko is an e-book reader application for the Android operating system. It supports the EPUB industry standard format for digital publications and incorporates facilities for browsing online catalogs on thousands of books (including thousands of free public domain work) and downloading them directly into the users personal library. The application features a bookshelf-like user interface that lets user navigate their collection of eBooks. It also provides a customizable reading experience through configurable font and background color, font size and type, margin size, display brightness, page turn mode, etc. Additionally, the application allows users to import their own books to read them on the go. »

Bluefire Reader is your go-to reading application for ePub and PDF content, including ebooks from most online book stores and leading libraries around the world. Bluefire Reader includes support for eBooks protected by Adobe Content Server.