Bookling is a simple eBook manager designed to make reading fun. It allows you to store, manage, and read your eBook collection on a desktop computer. It features multiple views for your library, multiple bookmarks, customisable fonts and colors for your book's text, and the ability to store your book collection in your choice of directory. Its back end is cleanly separated from the front end, allowing developers to easily port it to other platforms with a native GTK+ or WPF interface.
BookONO eBook Manager is an e-book manager and convertor designed as a compliment to Calibre. It is not a rewrite of Calibre, but instead an alternative product which makes some different design decisions. It uses Calibre to do a lot of the heavy lifting, so despite being an independent application, it is considered complimentary to Calibre.