Why was Harry Potter so successful?

It's a simple question,
Why was the Harry Potter series so successful?

I mean, it didn't add anything new to the genre, and there are a lot of other better series, with better character development and what-not.

I'm not saying its bad, but what makes an almost average book so popular?

>>9
No. The book sold poorly for some time after release. It was only because it was initially sucessful that the marketting push followed. Quite frankly it is because it meets a certain writing standard that anyone has even heard of it. Unlike the FOX network most publishers do not push books by first time authors for no good reason.
There's always going to be something better than whats popular out there. And there's always going to be a group of people who do not like the popular thing for whatever reason. The fact is the Harry Potter series appealled to a broad enough group of readers that it sells well, and continues to sell well, contrary to popular belief you really cant sell crap just by pushing it hard, it doesn't continue to sell and requires unfeasible investments especially for publishing houses who dont run on the highest margins.
Another thing being that the Harry Potter movies and associated wave of extraneous products came considerably after the books became popular, given that theyre not exactly a challenging read for the most illiterate of people i should hope the vast majority of its popularity comes from the books not the movies.