excuse me? that was extremely unnecessary and insulting.
harry potter is extremely popular... more popular than you could imagine.
its one of the greatest fantasy worlds in existence, alongside the lord of the rings.
rowling is a VERY respectable author and her series is highly respected, as well.
the series deals with quite alot of mature topics, theres nothing "prepubascent" about it.
if you want something really bad, look at stephanie meyer's twilight series... that may be popular, but its fanbase consists of people who either think its so terribly bad that its incredibly funny to read and make fun of, or teenage girls, and even some boys, who take it as seriously as meyer... who, by the way, actually threatened to leave her husband if her characters show up at her door one day... just to give you a taste of her mental stability.