PaterAlf: From my experience most kids don't like Pratchett's books very much.
I guess that's because they are some kind of meta-literature. They are not really fantasy books, but make fun of the genre and it works best when you've already read a lot of fantasy literature (especially books that use a certain standard formula).
Older kids and adults tend to love Pratchett's humour, younger kids'd often don't get the joke.
Hurm on reflection, you're completely and absolutely right. Pratchett is for a more genre-saavy reader that is already familiar with the tropes of the fantasy genre and will enjoy a hilarious deconstruction of them. That precludes children, but it's perfect for teenagers who've already read Tolkien or played some D&D.
I liked how simple and straightforward the first Potter books were, it doesn't delve into complex issues and thus it's perfect for children. Wizard society, makes pretty much no sense and ran exclusively on the power of plot, but that was ok. Later books when some of the interaction between muggles and wizards was explored, the whole thing fell apart at the seams.
