Adam Gopnik gives a great overlay of fantasy for young adults in this week's New Yorker. He gives great insight into the success of Twilight, Eragon and The Lord Of The Rings.
"Books win their audiences for a reason. Most popular books wear their artlessness on their sleeve: Stpehenie Meyer, the author of the "Twilight" series, is an awkward writer with little feeling for construction, but the intensity of emotion with which she imbues her characters is enviable. You never doubt her commitment to the material, which is half the battle won."
"one might mock--one does mock--the master of what is, after all, mere mock history. But the fantasy readers' learned habit of thinking historically is an acquisition as profound in its way as the old novelistic training in thinking about life as a series of moral lessons. Becoming an adult means learning a huge body of lore as much as it means learning to know right from wrong. We mostly learn that lore in the form of conventions; how you hold the knife, where you put it, that John was the witty eatle, Paul the winning one, that the North once fought the South. Learning in symbolic fomr that the past can be mastered is as important as learning in dramatic form that your choices resonate. (!)