Harry Potter? That's about witchcraft, isn't it? And witchcraft is as the sin of rebellion, isn't it? And that's like, bad, isn't it?
Okay, I'm being goofy and backwards, here's the real deal:
1 Samuel 15:23
For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry. Because thou hast rejected the word of the LORD, he hath also rejected thee from being king.
It is unwise for Christians to get in to this stuff. Harry Potter is tame material, but it is opening the door in the minds of millions of young people. The question yet remains, what is coming next for which the door has been opened?