Are you aware that you can vote on books other readers have submitted?  This allows you to voice your opinion on a book without having to leave a comment.

First Log In and then click on the Browse Books tab.  At the bottom of each reviewed book there is a set of stars.  Move your cursor over the stars of a book you have read and would like to rank.  If the stars turn green, you have not yet voted on that book.  If the stars remain yellow, you have already ranked that book in a previous session.  Your votes are automatically tabulated.  Top vote getters can be viewed on my side bar under Highest Rated.