October, Greatest Month of All Time, offers many riches including but not limited to: animals in Halloween costumes, dying leaves that remind you of your mortality but are so pretty you don’t really mind, pumpkin-spiced everything, and, best of all, lists of horrific books!

Below, I’ve gathered up a by-no-means exhaustive list of books dealing with possession, personality shifts, and the paranoia that sets in when your friends are replaced by demons, aliens, and even robot-duplicates… If I’ve missed any of your favorites let me know in the comments!

The Rains by Gregg Hurwitz

When a meteor strikes a town called Creek’s Cause, formerly reliable adults are transformed into savage monsters. No one over 18 can be trusted, and parents stalk their own children like predators going in for a kill. Brothers Patrick and Chance Rain manage to escape and find refuge in a school with a few other fugitive kids. Now they might be able to look for answers, and maybe even cure their loved ones. But there’s one terrible problem standing in their way: Patrick is only days away from his 18th birthday.

Can Chance find a solution before his brother turns on him? And if their enemy is truly alien, how can they ever hope to fight it?

My Best Friends Exorcism by Grady Hendrix

High school sophomores Abby and Gretchen’s longstanding friendship hits a rough patch when Abby begins to suspect that Gretchen has been possessed. Set in 1988, during the Satanic Panic that had Americans looking for Satanists under every heavy metal album, Gretchen’s personality shift may signal more than an influx of hormones. As Gretchen slides into new shades of moody and irritable, she also seems to attract all sorts of weird phenomena—from the owls who suddenly surround her home to the mysterious odor no amount of Benetton perfume can mask. Abby will do whatever it takes to find the truth behind her BFF’s behavior, even if no one else believes her. Will their friendship prove stronger than the forces of Hell itself?

The Cipher by Kathe Koja

In Evil Dead 2 (Greatest horror comedy films of all time? Greatest horror comedy of all time.), Ash’s hand is possessed by the Deadites. Raimi and Campbell play it for absurdist comedy—instead of losing his soul or personality to a demon, only Ash’s hand is possessed, leading to a slapstick battle with the evil appendage. I’m bringing this up because a similar thing happens in Koja’s The Cipher, but with far darker results. Nicholas and Nakota, a pair of depressed would-be artists, find a hole in their closet floor. But the hole doesn’t lead anywhere—it’s simply a spot of nothingness, “not the absence of light but living black”. At first it’s all fun and games when they throw things into what they call the Funhole, but when Nicholas’ hand goes in… well, things get a whole lot more serious.

The Exorcist by William Peter Blatty

Blatty based The Exorcist on a real case but changed some fairly significant aspects for his novel: rather than coming from a Spiritualist/Lutheran family, poor possess Regan O’Neill is the daughter of an atheist actress, who at first seeks every secular cure for her daughter before turning in desperation to the Catholic Church. Blatty also chose to make Regan a girl rather than the young boy known as Roland Doe, which allowed him to go into some pretty icky sexual territory in the possession scenes. Finally, while this is certainly a story of possession, it’s also a story about religious faith lost and found, as both Regan’s mother and doubt-addled Father Karras have to confront the mysteries of the universe and the nature of evil.

Plus it’s also freaking terrifying.

Pandemonium by Daryl Gregory

When is a possession story also an alt history? When it’s Daryl Gregory’s Pandemonium, in which an alternate 1950s U.S. is suddenly beset by what can only be describes as an outbreak of demonic possession. But wait, there’s more: some of the demons also seem to be embodiments of pop culture archetypes: the Kamikaze, who goads people to suicide; the Captain, a brave soldier who bears more than a passing similarity to a certain Captain in this timeline; the Truth, who targets liars.

Our protagonist, Del Pierce, thought he’d been cured of his own possession. Then one day The Hellion, a trickster whose pranks can be fatal, turns back up in his life. What’s a young demon-possessed man to do? Why, head off on a quest to find that timeline’s version of Philip K. Dick, of course! Or at least to find VALIS, the demon who’s currently inhabiting Mr. Dick… But can even a legendary sci-fi writer’s personal demon save a man possessed?

Who Goes There? by John Campbell

John Campbell’s classic novella, first published in Astounding Science-Fiction in August 1938, set the standard for a sci-fi possession story by beginning with a tense setting and making things worse from there. A small group of scientists have already been living in freezing isolation during an Antarctic winter when they find an alien spaceship. The alien pilot begins systematically devouring and impersonating members of the research group. The story becomes a constantly twisting nightmare of paranoia, as each scientist suspects the others of harboring the Thing, and the men begin to go mad as each realizes he might be the last human left in the station. “Who Goes There?” has been adapted four times, most famously in 1951 as The Thing from Another World and again in 1982, by John Carpenter, as The Thing.

The Terror, by Dan Simmons

Dan Simmons is probably best known around these parts as the author of Hyperion, Ilium, and Olympos, but in 2007 he wrote a taut survival story/horror story that carries an element of possession! Based on Sir John Franklin’s 1840s Arctic expedition, Simmons follows the crew across the ice as they begin to succumb to snow-blindness, frostbite, and starvation, and rebellion and cannibalism are never far away. But even worse, the crew begin to believe that they’re being stalked by something that might be a polar bear… or it might be a demonically possessed polar bear.

The Body Snatchers by Jack Finney

Originally serialized by Colliers Magazine in 1954, Jack Finney’s The Body Snatchers was published as a sci-fi novel in 1955 and quickly became a bestseller. Mill Valley, California is invaded by space seeds who replace people while they sleep. As the humans crumble into dust, the seeds grow physical duplicates from giant pods. Obviously, just the elevator pitch of this novel is terrifying, but what made it work was the creeping sensation on the part of the non-pod people that their friends and neighbors were…different. The novel has been adapted into four different films, with both the 1956 and 1978 iterations considered classics of sci-fi cinema.

Come Closer by Sara Gran

When Amanda was a child, she, like most kids, had an imaginary friend. Lately she’s been dreaming about her friend again, except now the little girl has grown into a gorgeous woman…who has sharp teeth, and enjoys cavorting beside a sea of blood. In her waking life, Amanda keeps hearing inexplicable noises in her apartment, She finds that ordinary notes to her boss are filled with obscenities she can’t remember writing, and that a voice in her head goads her into shoplifting and smoking again after having quit years earlier. Is she losing her mind? Or could the impossible be true, and her invisible friend has returned as an eons-old demon?

Sara Gran’s second novel balances between psychological suspense and outright horror as her narrator mulls the nature of madness and possession, and fights to take her life back before it’s too late.

The Stepford Wives by Ira Levin

The Stepford Wives is not only a feminist classic, but also a story that digs into how terrible it is when someone you thought you could trust goes through a terrifying personality shift. Joanna Eberhart is a New York City photographer who decides to relocate with her husband and kids to Stepford, Connecticut. She’s disturbed to find that all the other wives in Stepford are not just polished and beautiful, but also alarmingly submissive to their husbands. The book becomes a twist on a possession tale as Joanna’s independent friend Bobbie seems to fall under the same spell as the other wives. IS the Men’s Association behind this? Are the women even human anymore? Will Joanna be next?