I must disagree. The Hobbit is certainly childish, but it was written as a children's story. LOTF conciously avoids the more childish aspects of The Hobbit, keeping only those it has to to maintain a consistent story line. Harry Potter is DEFINATELY childish.
I guess you could describe the simplified, black-and-white distinction between good and evil in LOTR as childish, but that's common to most fantasy. The main themes are temptation and sacrifice, which are hardly childish. The fact that Sauron was defeated by a hobbit, the weakest creature in the world, and not by heroic force of arms, is also telling.
I haven't read either of those other books, so I can't compare against them. |