Try gooodreads. The phone app works in conjunction with an account on the web. You can have different lists (virtual bookshelves, natch). The first one I used was called SnapTel - the focus of that one was that it shows you where a book is available and shows prices, so you can stand in the bookstore and comparison shop! But I like the features of goodreads for managing my read/want/currently-reading, etc. lists. It's kind of a social network, too. You could be my 2nd goodreads friend, after my W. I just haven't bothered to add anyone. LOL.
