Calibre is an e-book library manager. It can view, convert and catalog e-books in most of the major e-book formats. It can also talk to a few e-book reader devices. It can go out to the Internet and fetch metadata for your books. It can download newspapers and convert them into e-books for convenient reading. It is cross platform, running on Linux, Windows and OS X.
For screenshots: http://calibre-ebook.com/demo
For installation/usage instructions please see