Why? because the book contains well-known patterns and does not really have its own universe. I understand those who have compared him to Tolkien. The characters are not actually typed, the story is fairly linear and especially, if the beginning of the book is nevertheless quite rhythmic, there really was a decrease of rhythm and after 100 pages, is a bit behind. The problem is that when the action is introduced in the book, we almost know beforehand what will happen and we can not really say that one is surprised.
In short, if you are honed to the fantasy, you easily read, you have a good time but it will remain nice. Well, we still highlight the great performance of this work given that its author was only 15 when he wrote it!