From Buffy the Vampire Slayer to Carrie, pop culture has gotten a lot of mileage out of the idea that high school is the stuff of nightmares. But what if high school wasn’t so bad, except for the part where you literally had to go to hell?

That is, more or less, the premise of Curse of the Evil Librarian, Michelle Knudsen’s conclusion to her Evil Librarian trilogy. After demons tried to invade their school and their summer camp,Cyn and Ryan have to visit the demon world to face the once-again resurrected Mr. Gabriel on his home turf.

That doesn’t mean the story is all horror, all the time, though. “The only way I could write something scary, I think, is to know that I'm going to be balancing out the horror with humor,” Knudsen says. Cyn’s signature voice is fully intact, as she wryly comments on everything from the demons’ many appendages to the musical Cats.

The horror mostly comes from the demons and their diabolical plans, leaving the high school drama refreshingly low stakes. “There is so much YA fiction where high school is this battleground, and that wasn't my experience,” Knudsen says. “I loved high school, my friends from high school are still my best friends, and it was not like every day was a unicorn party, but it was generally a good time.” Cyn has enough to worry about without bullying mean girls or threats of expulsion.

As absurd as the series often is (a major plot point in the first book revolves around how much demons love the musical Sweeney Todd), the villains are genuinely frightening—especially the titular evil librarian, Mr. Gabriel. “Underneath all of the campy stuff, I did want him to actually be like a real threat and really bad,” Knudsen explains. He not only curses Ryan and brainwashes their friend Annie, but also murders a whole bunch of people.

Mr. Gabriel is a classic abuser, manipulating his friends, family, and even enemies into helping him while convincing them it’s for their own good. (It isn’t.) Figuring out how to navigate these types of relationships is a vital part of growing up. “Even if it's not an abusive relationship,” Knudsen says, “it can be hard to figure out where your boundaries are and to figure out what you're comfortable with and what kind of behavior is OK and not OK.”

With most of the characters romantically paired up, they all have to struggle with the question of how to be good partners. Cyn, in particular, continues to struggle with her tendency to hide things from her loved ones, ostensibly for their own good. What she has to realize, Knudsen says, it that “even if she is convinced that she always knows the right thing, it's not up to her to make decisions for everybody.” Each of the characters has their own role to play in bringing down Mr. Gabriel once and for all.

Although the book’s ending is somewhat open-ended, Knudsen insists it’s just because that’s how real life is. She has no plans to revisit these characters. “It’s hard to get to know characters that well and sort of spend all this time and get so invested in their stories and what's happening and then just let them go and feel like they're sort of on their own from this point on,” she says. “It's a weird, weird feeling.”

Alex Heimbach is a writer and editor in California.