It's amazing when things happen that the world outgrows books. Now Harry Potter is not just a series of books or films. It's a real
big world that has many components and already lives itself. There are theme parks, places, quests, excursions related to Harry Potter, and
books are being published - and not fiction, but, for example,
on cookery and knitting. It's a unique phenomenon.
It's also surprising that the first generation reading about the boy who survived grew up with him, As Harry and his original audience grew older, the maturity level of the books "grew" as well, so while the early books are straight children's literature, the later ones are much more serious.
And now there's
Pottermore - the real official resource of the Harry Potter world, run by J.K. Rowling herself, where you can read details of the current lives of the franchise's characters, who (well, what if?) live in their own parallel world and play Quidditch there.