My ratings are based on a lot of things, including personal thoughts, characterization, plot development, and creativity. Usually I use the following scheme to rate a book on my review:
Love it, and recommend it to everyone. Pure perfection!
Really liked it, but the book had some minor flaws that couldn't go unnoticed.
It was OK, but for some reason I couldn't connect with the characters or the story. Probably wouldn't re-read it.
Hated it. Not a book that I would recommend.