I didn't jump on the bandwagon when it passed by. I came to HP because I was interested in knowing why my daughter did it. It was a parent thing, I also had to provide them the books. But I'll tell you why I kept to it since both my kids have now gone on their own.
First, you get to identify your kid self in the struggles HP goes through, especially if you've had it bad in school. Second, her writing is good, concise and her images so very imaginative. Third, JK's a master 'plotter' , the plots are so good as to keeping you guessing almost through the book with barely a hint. Fourth, things go so fast and nice that you won't dare leave in the middle of such a captivating story. Last of all I WANNA KNOW HOW IT'S GOING TO END!!?!!!?!!