I have read all of the Harry Potter books and found them to be entertaining and wonderfully written. I was sucked right into the world of Harry Potter and the rest of the cast. I will not pretend to be able to write a clear and concise summary of the series and how it relates to some of the concerns that some Christians have put out there. What I will do is point you toward two that have. The first is by Jim Hamilton and the second is by Andrew Peterson, contributor to The Rabbit Room.
I came across this great review of the series and its response and rebuttal to some of those concerned about the series.
Here is another very well written defense of Christians reading the Harry Potter series.