The Kindle app allows you to get thousands of books right on your phone. Even some free ones. You can access the kindle store and buy books off their without having to own one. There are over 900,000 book out there.
NOOK: Read eBooks & Magazines
This app allows you to shop for thousands of books through Barns and Nobel. Not only can you access books, but also magazines and newspapers.
Kobo Books – Reading App
Not only does this app allow access to thousands of books, but it will track what interests you have in the kinds of books you read. You can save favorite quotes, add books to your library through your email and lastly you can transfer the book on your phone to any other electronic device you have.
This allows you to have full control over all your app functions. While reading, you can customize your visual options such as line spacing, size of font and bolding etc.