I have been using this app for a couple days after using audible for about a year. It works well when playing books, but does not appear to have the little extras that audible does. For instance, I have not found a sleep timer for the book playback, it does not appear to let you start listening to books as you are downloading them (I have only downloaded 2 books so far), and it is also not as easy to browse through book options as audible. That said, if you just want a basic audio book player, this app works fine.
CKM79 about Audiobooks.com: Get audiobooks, v5.9.4