I really like the idea. I often will buy books, intending to read them (someday), and then promptly forget that I have them. This would be great for that, and I like the past stats for how many pages/books I've read.
Here are some notes I took while playing with the site:
1. It would be great to have a way to add multiple books to your queue at the same time, or at least to not have to re-do your search after you've added a book. Especially when you're loading in a back-log.
2. Have more than 10 search results.
3. If you hit the back button, after a book has been added, you get the book twice. (It happened when I added Anathem to the 'will read' list.)
4. Make Author name clickable, so it shows a list of books by that author.
5. Why would I want to edit the description/title/author of a book that's already in the system? I think you might consider making this an admin function and have a way to submit changes, rather than letting users deal directly with that.
6. It would be great to have a recommendation system, or maybe more orthogonal to the system would be to specifically recommend someone's next book. I know I often have problems deciding what my next book should be.