I have a sad admission to make. Many years ago I thought that Harry Potter was evil because it promoted "magic", and that's spoken against in the Bible. As a Christian, I'm supposed to avoid those things and so I condemned those books and movies. It even got to the point that my mother-in-law, a pastor's wife, got rid of her Harry Potter movies because of what I and my wife (her daughter) were saying.
I was wrong. And ignorant.
After becoming involved in Fans For Christ I started getting to know people who loved Rowling's works. Then I broke down and watched the first movie. I loved it! And I didn't see anything Satanic or evil in it. My wife and I began watching the other ones, and then I started reading the novels. I am now an official Potterhead, and have begun dressing up as characters from the movies and books (mostly myself as Professor Lupin and my wife as Tonks). This past year at Dragon*Con I even gave a sermon with a Harry Potter theme and preached with my wand, dressed as Lupin.
So why the change?
I realized that the books didn't actually promote paganism or real-world evil spells. In those books you are either born a wizard or you aren't. If you aren't one by birth, you can't learn how to become one. It's a form or genetics as well as technology. The Bible speaks against magic in the real world, but doesn't fully define it. The idea usually comes about that any supernatural powers not from God are automatically from Satan. In the real world I can't disagree. But fiction follows different rules and settings than our own. In these stories you either have deities other than our God, or you have something like Harry Potter where the power is innate and not reliant on a supernatural being.
That brings me to an article I recently read, surprisingly found on Crosswalk.com. It deals with this very issue, and states the topic in a way that I can't say any better. So I'll just highly recommend that you go and check it out. For any Christian it is an important read.