This sounds like a great idea to me, it should make it easier to get a feel for the popularity of a book while clearly separating the voters opinion of the review and their opinion of the actual book. I agree with you that each book having its own node and being able to reply to that would be a good format. However, I think there are also a couple details with this that should be are worth discussing:
- Should voting on the books themselves use up any of your votes?
- Would we want to see the rep of the book before voting? Or would this lead to people downvoting it not because they didn't like it, but because they don't think it's worthy of it's current rep.