USA Today says look out, Harry, here comes Narnia, but I've heard at least one bookseller tout Christopher Paolini's Eldest as the real threat to Master Potter. Of course, USA Today has good reason to be predicting success for the C.S. Lewis series: HarperCollins has 167 Narnia-related titles to sell, as The Lion, the Witch & the Wardrobe will be re-incarnated as a Disney movie in early December.
Keep an eye on Eldest, which debuts in August; it's the sequel to the best-selling fantasy Eragon, which is also being made into a movie as we speak. Last year Ann Hulbert at Slate wrote about child-prodigy authors like Paolini, who began writing his series when he was 15.