Fiction by Lev Grossman.
Okay. So this book here is supposed to be a grown-up Harry Potter. Like, imagine if Harry, Ron, and Hermione went to magic school at age 17 instead of 11. And screwed each other indiscriminately and became depressed alcoholics in the bargain. Oh, and then what if they went to Narnia and ruined that place as well?
Yeah, that's what I thought.