Looks great! I wonder if it would be possible to import data from Goodreads; many people use Goodreads to keep track of what they've read, and what they're planning on reading. They wouldn't want to lose that information by switching.

Giving authors tools for self-promotion is also a big deal -- and something many authors actively engage in with Goodreads.

One more thing, that should be higher priority: The ability to add books to the database. There's nothing more frustrating than wanting to add a book to a shelf, and not being able to! (Maybe it's already an option? If so, it's not easy to find.)