Strictly speaking, Passion Hunters is sixties sleaze, but it could be considered horror of a sort. In fact, it has a lot of interesting parallels with Roman Polanski's 1968 horror masterpiece Rosemary's Baby. The couples are almost identical at the beginnings of both stories. Attractive, newly married, not as innocently depicted as a fifties couple might have been, but still quite traditional--the husband is the husband, the wifey is the wife, and it goes without saying that some day they'll have children.
Rosemary and Guy move into an apartment building with a dark history of devil-worship, and fall under the influence of an evil coven. The difference in Passion Hunters is that Gwen and Pete move to the suburbs, and their lives are taken over not by satanists, but swingers! In both cases, the husbands plunge right in, and the wives are plunged into nightmarish chaos and confusion. After Gwen's and Pete's first neighborhood orgy party, she "felt as though she and Pete had visited briefly in another world, a strange and disturbing and frightening world." After her first lesbian encounter, she "was appalled and frightened at what had happened."
Passion Hunters is written from Gwen's point of view, and the most surprising thing to me about it was how joyless and downbeat so much of it is. She watches in horrified dismay as her husband lets the sexy redhead across the street seduce him, and as he goes deeper and deeper into the swinging lifestyle. He expects her to embrace it as enthusiastically as he does, and often loses patience with her Kentucky-bred scruples. They spend a lot of time arguing, and he spends a lot of time sleeping downstairs on the couch while she cries alone in their bed. The situation is complicated by the fact that the whole neighborhood is in on the swinging, and by the fact that Pete's boss is the ringleader. At one point, as Gwen and Pete argue, she demands, "Pete, do you really want me to make love with Larry--to get you a promotion?"
Actually, that point is somewhat moot, since she's already had steamy sex with Larry at an orgy, right after an equally scorching encounter with another husband from down the street:
Then she opened her eyes, because she sensed someone else was there. Over Don's blond head, resting on her breast, she saw the dark gleaming face of Larry Crawford. He was gazing at her, and she sensed at once that he had been there in time to see the end.
A hot flush blazed through her, the blood racing through her body. She tried to raise up, but Don's limp body pinned her down.
Larry waited. Don moved, sat up, rubbing his face, yawning.
"I'm next. Scram," said Larry to Don, pleasantly.
"Right-o." Don yawned again widely. "She's great. Just great." He patted Gwen's hip affectionately, and got up off the bed.
Despite the euphemistic terms and coy phrases, there's a lot of sex, and it's described in vivid detail. Gwen gets caught up in it often enough, and lets herself go in the moment, but the harsh self-recriminations that inevitably follow really throw a wet blanket over everything, and ruin much of the eroticism.

The biggest downer of all is when the redhead's mousy husband has a fit of pent-up jealousy and almost kills her (the redhead, not Gwen). It's a repulsive, bloody scene in a novel that I expected to be light, fun, and sexy. The callous, indifferent reactions of the other neighbors throw an even more sinister, almost coven-esque light on them:
"Oh, she lost some blood, that's all. Larry bailed Floyd out of jail and sobered him up. Why in the world did you call the police?" Don looked genuinely puzzled. "We could have handled all of that."
I guess the ending is supposed to be a happy one, with Pete changing jobs and returning to Gwen's loving arms, and both of them moving back to the safe, baby-friendly environment of town ("Nice houses, near schools and shopping centers") where they mean to start a family. At least they've learned how to enjoy sex with each other, and the novel ends with them in bed putting good use to their hard-earned knowledge and experience.
I knew I had to have this one after seeing the cover scan at the Vintage Paperbacks site. The painting is by Fred Fixler--read about him
here. If you want to check out more related covers, see the
Robert Bonfils and
sleaze galleries (good luck hunting down any for sale, though!).

HEY, LET'S MAKE LOVE: If they'd moved to the suburbs, the couple from Rosemary's Baby could just as well have been The Passion Hunters.