What is it about Harry Potter that lends itself to trivia contests by child genuises?

Last night my 12-year-old son was talking with another boy he'd just met. They spent an hour asking things like, "How many points do you get for throwing a book through Moaning Myrtle's stomach?" (Moaning Myrtle is a ghost in the story.)

Now, I read those books three times, and I didn't remember half the situations they were discussing, and I knew almost none of the answers!

I've seen my son have these kinds of trivia challenges about Harry Potter with a number of kids. I never cease to be amazed by the recall of minor details from the story.

It's really fun to watch, even though I can't quite understand it!