I would say that the books are geared towards children much more than the films are. Kinda how you have to 'be into comics' to enjoy them - I think you have to 'be into children's fairy tales' to enjoy the HP books. Again - only having read one - but I stopped at the 2nd one because it wasn't 'mature' enough for me.
I could be wrong, though, because I also think the first 2 films are quite family-oriented and the latter ones have some darker imagery/themes. Could be a reflection of the books getting more serious as well.
Wait, isn't this a Star Wars thread?