On Harry Potter (and Choices) - I
I am not about to argue that the series in general or any book in the series in particular presents the gospel. From that sense, if we are gospel focused, one might argue that investing time in reading the series is not profitable. While I think that is an extreme position (I heartily recommend the answer from D. A. Carson and Tim Keller on what causes fragmentation in the church today - bottom of the list as of this writing) that would lead one to nearly all fiction, whether written or otherwise, I see it as a defensible, though not correct, position.
Others would argue that it is not that the books are fiction, but that they deal with magic in a positive light. In the series, there is normal magic that is acceptable and then there are the dark arts. Many Christians would argue that the Bible knows nothing of "white magic" and that all magic is "dark" magic. In his book A Visit to Vanity Fair Alan Jacobs includes an essay titled "Harry Potter's Magic" in which he lays out a case for why the series is acceptable reading for Christians even though witches and wizards are the focus of the series. The normal magic in the Harry Potter books is not typically divination, but is a cousin to technology. Instead of a dishwasher, one uses a wand to clean dishes. But there is also a recognition (one significant scene in the last book stands out in this regard) that some tasks call for doing the hard work instead of taking the easy (magical) alternative.
To consistently reject the Harry Potter series because of magic requires that one also reject Tolkein's Lord of the Rings. There is no legitimate argument that there is a substantial difference between the magic in The Lord of the Rings and the magic in Harry Potter, between, say Gandalf and Dumbledore. Lest we forget, in Tolkein's work Aragorn brings an army of the dead to fight against Sauron's forces.
So one could reject Harry Potter due to series focus on magic. One might be concerned that the series would make readers want to investigate wicca or other occult practices. However, doing so would also require that all books containing a positive view of witches, wizards and magic likewise be rejected.
I understand the basis of the argument, but do not agree. These novels (both Rowling's and Tolkein's) are clearly fictional works, as evidenced by the names of most of the characters in the Harry Potter series. Also, as Jacob's noted in his essay, in Harry Potter's world you either are born with the ability to do magic or you are not. One does not acquire the talent to do magic through investigation or practice. The seeming majority of the world simply cannot do magic.
I have dealt here with some objections as to why Christians should not read the Harry Potter series. I will continue with a discussion of why I think there is benefit in reading the series. But one final word: if your conscience tells you not to read the books, do not read them. Any benefit is not worth an offense to your conscience. If you have a friend who does not think they should read them, do not push them on your friend and thus become a participant in offending your friend's conscience. Finally, I encourage those who do not think Christians should read the books, do not look down on those that do read. You may, gently and in love, present why you think we should not, but do not let it become a wedge.