It's basically a gender-swapped (irony) Worst Witch.
Probably, anyway. I dunno, I read the first 3 or 4 books (they were the only ones released at the time) and thought it was a steaming pile of garbage, the first one especially filled with continuous deus ex machinas to get the main character through problems he otherwise didn't have the skills to solve. It's the only one I really remember because I was forced to watch the movie too... and play a PC game of it.
So I suppose one of way of looking at it is there must be something to the world-building, because it certainly didn't get so popular because of the storytelling aspects.