calibre - Ebook manager, viewer & converter
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
Apple Books - The all-new Apple Books has been redesigned to make finding, reading, and listening to books a beautiful, effortless experience on iPhone and iPad.
Amazon Kindle - Amazon Kindle software lets you read ebooks on your Kindle, iPhone, iPad, PC, Mac, BlackBerry, and...
Open Library - The ultimate goal of the Open Library is to make all the published works of humankind available to...
LibriVox - free public domain audiobooks