I don't really like just rating my books, mainly because even if I love two books, i can't give them both 5, or 4 stars, they need relationship to each other at the 5 or 4 star mark, but decimal point a are garbage as you may have hundreds of 4 star books. This is wher I think a tier list supported rating system would be interesting, allow users to create a tier list of their books, 5, 4, 3, 2, 1, DNF; this would also create a very interesting system for recommendations. For example, my 5 star books could make a hash, all similar hashes that fall in the same bucket within a expected range, probably have a book that i would be interested in.