You’re in a flimsy tent, tucked deep into your sleeping bag. A dime-store flashlight is jammed between your chin and shoulder, the dim beam pointed at the dog-eared pages of a paperback horror novel. When a twig snaps outside, you pretend not to hear it. But the night is long, and you drank too many beers around the campfire. You can’t hold it until dawn. And when you finally unzip your tent and clamber out into the chilly, starry night, you desperately try to forget the horror novel you were just reading. You stumble blindly toward the nearest tree, bare feet barely avoiding sticks and thorns, and the last thing you want to think about are hillbilly cannibals, hermit rapists, man-eating plants, or genetically enhanced monkey monsters.

That’s right, Campers. Spring has officially arrived. For those who prefer their great outdoors served up with a side of horror fiction, the following five novels will leave you squirming in your sleeping bag.

The Ruins (2006), Scott Smith

The power of The Ruins lies in Smith’s ability to take an enormously silly premise––killer vines trap tourists on an ancient Mayan ruin––and make it somehow believable. And while Carter Smith’s 2008 film was a successful adaptation in a variety of ways, it doesn’t quite capture the bleak futility of the incredibly imaginative novel. From the oppressive heat of the Mexican jungle, to the tequila-fueled dehydration of its characters, The Ruins is the rare book that paints a setting so vivid, it puts you there.

Camping Callbacks: Features what may be the coolest campsite of all time…if you’re willing to ignore the acidic, man-eating vines.

Watchers (1987), Dean Koontz

Those who feel the prolific Koontz has lost a step in recent years should revisit Watchers, which saw the bestselling author at the top of his game. Revolving around a trio of Koontz’s favorite subjects ––the outdoors, genetic mutations, and guns––the story has a young military vet joining forces with a intellectually-enhanced golden retriever to defeat a mutated baboon creature developed for government warfare. Published before everything Koontz put on paper automatically dominated the bestseller lists, Watchers was later adapted into a regrettable Corey Haim vehicle hampered by shitty production values. It‘s one property that‘s genuinely deserving of a remake.

Camping Callbacks: Nature hikes, a canteen full of orange Kool-Aid. The final showdown takes place in a mountain cabin as Koontz gleefully piles on the gun fetishism.

Off Season (1980), Jack Ketchum

Published in the wake of 1977‘s The Hills Have Eyes, Ketchum’s survivalist horror novel certainly bears more than a passing resemblance to Wes Craven’s hit shocker––both are loosely based on the Scottish legend of Sawney Bean, a notorious cannibal leader from the 1400s. In Off Season Ketchum sends a forgettable cast of stock characters to a secluded island to be pursued and devoured by a horny family of inbred cannibals. After initially defending their cabin in a Straw Dogs-type scenario, the heroes are eventually chased into the woods where the action regresses into pure, unadulterated savagery. Offspring, Ketchum’s 1991 sequel to Off Season, was adapted into a 2009 film from Ghost House Underground.

Camping Callbacks: A remote mountain cabin on a forrested Maine island. A few strangely specific campfire recipes involving human flesh.

Trapped (2010), Jack Kilborn

Arriving a full thirty years after the release of Off Season, Trapped reads like the long lost twin of Ketchum’s cult classic––both novels feature victims camping on a secluded island overrun with mentally regressed cannibals. But Jack Kilborn (a pseudonym for author J.A. Konrath) makes some ballsy moves with his characters, resulting in something deeper and more compelling than the surface shocks of Off Season. Eschewing Off Season’s bland cast of white bread couples, Trapped has a married pair of juvie counselors camping with a diverse handful of delinquent teens, including a couple of gang bangers, a slutty meth addict, and a pudgy sociopath. It’s sort of like Nightmare on Elm Street 3: Dream Warriors, only gritty. When the cannibals come a-calling, each member of the group must make a choice regarding survival…and those choices become less obvious as the story progresses.

Camping Callbacks: All the accoutrements of Off Season, but with hot dogs and marshmallows and shit.

The Summer I Died (2006), Ryan C. Thomas

Thomas’s grim little chapbook of pain and anguish probably ranks as the most graphic entry on this list. Best buds Roger and Tooth want nothing more than to shoot some beer cans and smoke a little weed up on Bobcat Mountain. But when they come between a women in distress and the pervy hermit who has kidnapped her, their camping trip takes an immediate detour through Torture Porn Canyon. With loads of mean-spirted, stomach-churning violence The Summer I Died is an endurance test, even at a mere 154 pages. It’s certainly not for everybody. But if you want to freak yourself the fuck out on your next camping trip, you can’t really do any better.

Camping Callbacks: Beer. Weed. Guns. Bobcat Mountain.