MegaReader gives you access to almost 2 million books for under $2 bucks!
What a deal!
All of the books are going to be public domain books, or books offered by the publisher for free. So it's not giving you access to pirated books or anything like that. So many modern titles won't be available, however you'll still have access to many classics and other works you might not find anywhere else.
If you're looking for variety, options, and/or you enjoy reading classic works...
I don't think you'll find a better back for your buck, or rather $2 bucks ;-)
(Link to this page: http://bit.ly/2MillionBooks )