calibre - Ebook manager, viewer & converter
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
FBReader - FBReader is an e-book reader for various platforms. Features:
Wallcat - Enjoy a new, beautiful wallpaper, every day.
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
Splashy - Breathtaking, auto changing wallpaper app for macOS, Windows, Linux, iOS & Android