They are books. They were only ever books, and this is the amazing thing: they will stay books.
This is, in fact, the thing about books. You read them, and then you can read them again, and, if they are really that good, they are wonderful to read again. (Plus the movies are out on DVD now.)
Your childhood is not over because there aren't any more Harry Potter books coming out. Your childhood is over because you're 26 years old. The books are still there.