When reading fantasy books, I generally apply two arbitrary criteria that I have found useful in determining books I like. The first is I look for the willingness of the author to kill important characters — not secondary or briefly mentioned characters. I’ve always felt that to do so was brave and showed a willingness to push the story’s limits rather than following a predictable course. The second is actually from Aristotle’s Poetics. Summarized, Aristotle says the primary character must be believable. In essence, the character must be more human than superhuman.