What in the world does the Bible have to do with Harry Potter? Actually, I do know a Bible verse or two related to Harry Potter:
Now the works of the flesh are clearly revealed, which are: adultery, fornication, uncleanness, lustfulness, idolatry, sorcery, hatreds, fightings, jealousies, angers, rivalries, divisions, heresies, envyings, murders, drunkennesses, revelings, and things like these; of which I tell you before, as I also said before, that they who do such things shall not inherit the kingdom of God.
It seems pretty clear to me that Harry Potter is not something to be messed with. Certainly not the subject of a Bible study, unless it is a Bible study as to why you shouldn't be messing with it.
A lot of people have the opinion that you shouldn't be against the Harry Potter series if you haven't read it? I don't see how that makes a lot of sense. There's witchcraft in Harry Potter, right? That's all I need to know. Whether Harry Potter uses actual spells or not is irrelevant.
I'm not going to let my daughter (when she gets old enough) read the story precisely because of the subject material (witchcraft). I don't have to read it to know that it is not appropriate reading material. Similarly, I don't have to read Penthouse to know that that is not appropriate reading material. We all know what is between the covers, and it's not a knitting magazine, that's for sure. Even if, say, they make a computer model and put it in there... I don't want anyone in my family looking at a fake naked lady any more than I want them looking at real ones.
Harry Potter is hard to escape. Our library has a special display and a waiting list for the book. Advertisements are everywhere. Even some children's cartoons have references to Harry Potter like book series (I know "Arthur" has a Harry Screevner, I think Clifford has their own wizard series as well). The day will come when I will have to explain why I don't think it's an appropriate book for her. I don't need any Harry Potter Bible Studies making it more difficult.