Personally, I have never read the series or never intend to, as I am aware that it promotes witchcraft, sorcery, and homosexuality, which are an abomination in the sight of God.
The series also have names of characters that are actually the real names of demons or devils. Whether or not we call such things entertainment, we are still partaking in things that God hates.
Keep in mind these verses:
Colossians 3:2, "Set your affection on things above, not on things on the earth."
1 Thessalonians 5:22, "Abstain from all appearance of evil."
Leviticus 19:31, "Regard not them that have familiar spirits, neither seek after wizards, to be defiled by them: I am the Lord your God."
Deuteronomy 18:9-14, "When thou art come into the land which the Lord thy God giveth thee, thou shalt not learn to do after the abominations of those nations.
There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch.
Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer.
For all that do these things are an abomination unto the Lord: and because of these abominations the Lord thy God doth drive them out from before thee.
Thou shalt be perfect with the Lord thy God.
For these nations, which thou shalt possess, hearkened unto observers of times, and unto diviners: but as for thee, the Lord thy God hath not suffered thee so to do.
Ephesians 5:11, "And have no fellowship with the unfruitful works of darkness, but rather reprove them."
I think these verses answer your question.
Harry Potter: What Does God Have To Say