This is just too long to leave as a comment :)
Yes, I think we should apply Biblical principles to everything we read. This does not necessarily condemn the works of CS Lewis and JRR Tolkien. Not only is the ‘magic’ in the Chronicals of Narnia and The Lord of the Rings of a different kind, but the moral standards are different than the Harry Potter books.
I haven't read many of the Narnia books lately, so I will give an example from TLOTR series.
First off, it is simply not the same kind of magic. It IS called magic (JRR Tolkien said he couldn’t find any other suitable word for it) but it differs from the magic that is presented in Harry Potter.
The 'magic' is not accessible to just anyone. Gandalf was enabled to do things magically as he was granted this from "The One", who if I'm not mistaken is referred to as Eru. Don't quote me on that though.
There are no special incantations that makes someone magical. Those who got to close to the magic were effected in a negative way. Frodo was shaken, and 'was never the same' after his ring ordeal.
The things that were ‘magical’ were inborn with magic. The things in the Harry Potter series are enchanted or under a spell.
The power Gandalf had was NOT just the good side of a single force. There are bad guys who use bad power, and good guys who use good powed. No dark/light side of one force.
All this said, I don’t believe the ‘magic’ referred to in TLOTR is based on occultic magic as the magic in the Harry Potter books is. Same name, regrettably, but not the same substance.
Second, the morals in the LOTR are clear defined lines. There are good guys are good guys, the bad guys are bad guys. When one of the characters does something wrong or evil, there are consquences. When Harry breaks the rules or lies, he seldom faces consquences for them.
I must stress that I have NOT read an entire Harry Potter book. I have read material containing quotes from the books. This goes to say that if you feel I have been given incorrect information, please let me know, I will gladly recheck my resources if you can give me some specifics.
None of what I have written has even touched on the ‘grossness’ in HP books. While there is no verse in the Bible that says "do not read about gross things", it does put the ‘vile’ on the list I quoted from Revelation.