I have to disagree on her intended demographic. They were definitely meant for people the same age as the main characters, the early teens. And I think the first few worked well as "my first doorstopper." But you're right about her skills as a writer. And unfortunately, a lot of the people obsessed with the series now never branched out into other young adult fiction or moved on to more complex works as they grew up.

This is the best analysis of HP I've ever read.