Basil Wolverton's work has always been known as grotesque (one of the turning points of his career was winning a "draw the world's ugliest women" contest). Somehow though, these aspects never got out of hand as Wolverton's work had the fun and immediacy of all cartooning, if a bit more damaged. When he was drawing goofball sci-fi adventures like Spacehawk or boxing comics with Powerhouse Pepper the elastic faces and dark-darks made it more unreal and outrageous, but when Wolverton directed his pen towards the genuinely grotesque, as he did in his mind-blowing religious work like his depiction of the apocalypse or in these Twilight Zone-esque horror tales, the results get under your skin and the atmospheric lines become palpable.
Each of these stories follow the horror anthology "twist ending" outline almost to a fault. There's some good, smart storytelling going on here, but without Wolverton to illustrate them, well they wouldn't have been hunted-down and reprinted by Dark Horse more than thirty years later (Gateway is a reprint from 1988).
The "trick" for lack of a better word, of Wolverton's art here is to lull you into a kind of stupor of appreciation, where you forget about the kinda silly storytelling or rather, just let it sort of play out, and get caught-up in the sheer weirdness of the art. His lines are never ever straight, they're straight enough, but they always wiggle around a bit, and it makes even the simple contours of a room into a panel that you hold too close to your face and fall in love with. In another sense, at least in these horror tales, the bordering-on-sloppy artwork foreshadows the chaos to come. And when something crazy or creepy or scary happens, Wolverton's art is at its best as he draws every ugly detail but still in this zany style. Not quite the same, but a little bit like Rick Geary's work as Jesse mentioned, where the fun, cartoon-ishness of it makes it feels scarier and weirder. Look at the frame below from the titular story and the way Wolverton draws flesh slipping of a face:
Wolverton's people too are over-the-top and ugly, but they're ugliness comes from real-life. Every weirdo or creep looks like a weirdo or creep you could see or have seen in real-life. Old people say dumb stuff like "I wouldn't want to run into this guy in a dark alley", well, Wolverton draws pretty much everyone in a way that makes you think that. The brilliance in doing so is that since these are horror stories, you expect the villains or "bad guys" or whatever to be monster-like. Instead, they're just a little uglier, a little more crack-eyed, and wrinkled than everybody else, grounding it in a little bit of reality.
In "One of Our Graveyards Is Missing!", everyone's in a panic and looking stressed-out because somehow, the town graveyard's just a giant pit now, but a mysterious man seen near the graveyard moments before it disappeared has a particularly horrifying presence. His presence isn't that scary on its own, but how he enters the story and his context aid Wolverton's drawing and the story's atmosphere. The same weird feeling you get when you've read about a crime that's been committed and then you see on the news they've caught the guy. You're not sure if he's scary as shit because you know the crime he committed or if he's scary outside of that too.
But the story that's like, palpably horrifying and icky-feeling, is "They Crawl By Night". The story's about a guy who hallucinates night-time visits from these gross, crawling crab guys and then it turns out, hasn't hallucinated it at all (again with the trick horror comic endings). A great deal of this story happens at night and so, the interiors are darker but because Wolverton's work is all line and ink, the panels aren't necessarily darker, they've just got more shadow and even more lines which adds an eerie unreal feeling. Something I can't exactly describe makes these images come to life in that sense that you begin thinking about crab guys sneaking into your bedroom at night and say, lift your feet off the ground or close the nearest door to you.