calibre - Ebook manager, viewer & converter
LibreOffice - Writer - Open-source cross-platform word processor.
FBReader - FBReader is an e-book reader for various platforms. Features:
Microsoft Word - Microsoft Word is a commercial word document processor for Windows.
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.