I rate books solely within themselves. For example, Great Gatsby has 5 stars, but so does some of the Harry Potter books. Obviously, on a literary scale they don't even compare, but it is because I am rating them for what they are striving for. Within a series, I rate books within that series, not side by side with a similar series or similar books. So I hope you don't get uncomfortable when J.D. Salinger gets 3 stars at the same time Stephenie Meyer does.