Master Study of Fun-ness

I'm still studying Harry Potter, because I want to know how she sold so many copies.  Today, I am focusing on an intangible that directly contributes, I believe: how she made wizards so much fun.

Here are several instances in which Rowling cleverly defined the wizarding world, starting where I left off last time:

• "All I got were a few shrinking door keys and a biting kettle."
• "Well, dear . . . you'll find that [it was legal to enchant the car].  As long as he wasn't intending to fly [it]."
• Ron's posters of the witches and wizards on the Chudley Cannons.

I think these examples sum up very well the attitude she has toward making her books fun.  Food for thought.