My Best Friend's Exorcism

The thing with Grady Hendrix is that he always tells you the situation in the title. What it says is 100% what is happening. There is no actual doubt about supernatural events really happening or creatures really existing.
But his genius is in the fact that through the characters you still start doubting it. The events play out through a long time and so much of it is entangled with perfectly normal, everyday events that you will doubt yourself like the characters do.

Abby and Gretchen are best friends. Sure, Abby is poor and Gretchen is rich, but they still end up at the same fancy school (Abby through a scholarship) and they bond. For a time they are at the top of the food chain with their other two friends, Margaret and Glee, being cool and pretty and just doing all the things the right way.
Then one night, while they are trying supposed LSD at Margaret's weekend house... something happens to Abby. Something they assume is a horrible and ordinarily non-supernatural thing. But then things just get too weird to be a simple case of trauma.

The thing about Grady Hendrix is that so far, all of the books I have read by him were based around nostalgia and retro, but he approaches those things so great. Many times I feel those books try too hard and they also over-explain; they point out the references and why those things matter. Here we just get told about those things like they are natural. If you know, you know. I think that's the right way to do it, so it's not boring for the people who know, but the rest can still google those things, right? It just flows better.

His friendships are interesting as well. He never seems to pretend that friendships are always going great and they are perfect. In that way, he is much more realistic about human relationships, even if all his books seem to be about supernatural things. People aren't always kind.

Now, I will say, I don't think this is his best book, mostly because I prefer adult characters, but as far as teen ones go, they are pretty solid.