Many of us have read each volume of the Harry Potter series. While I've never lined up at the bookstore to snatch up a copy at midnight, I've throughly enjoyed the books.
For one thing, they are well written. Rowling knows how to tell a story. I especially enjoy her willingness to allow her characters (both young and adult) to grow, sometimes in surprising ways. Rowling creates characters we come to care about, so that when they hurt or die we cry. She also seems to have absorbed scriptures, mythology, and some of the best 20th century fantasy writers (T. H. White, J. R. R. Tolkien, and C. S. Lewis come to mind). Filtered through her own creativity, such sources (and no doubt many more I can not discern) have created a highly convincing world--the world of the wizards and assorted other magical beings and creatures.
Personally, though, I am most deeply moved by the deep themes she explores: the surprising power of willing and sacrificial love, the relationship of life and death, our reactions to fear, the importance of the decisions we make, the manner in which genuine community sustains us, the contrast between foolishness and wisdom, the allure of power, the ways in which evil ultimately harms itself, and the cost of commitment.
Frankly, such themes have deep roots in Christianity. Rowling, in my opinion, has created a very successful new wineskin for the gospel, as only a gifted and hard-working writer may do. I commend the books to persons of all ages.