calibre - Ebook manager, viewer & converter
Wondershare PDFelement - All-in-one PDF editor
FBReader - FBReader is an e-book reader for various platforms. Features:
Foxit PhantomPDF - Edit PDF files with our feature-rich PDF Editor. Download Foxit PDF Editor to convert, sign, scan / OCR & more. A speedy PDF Editor alternative to Adobe Acrobat.
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.