WELCOME to a land where "the clouds (are) like dark spills of Cool Whip" and those who live beneath these artificial-dairy- product skies switch cable television channels as they listen to friends tell horror stories about former marriages; say hello to brand names, rental cars and acute sensibility loss; enter the esthetically attenuated world of Frederick Barthelme's Tracer.

Tracer, Barthelme's second novel and third book (Moon Deluxe, a collection of stories, appeared in 1984, as did the novel Second Marriage), is a distinctly modern story cast in outline. It begins with Martin, just kicked out of the house because his wife, Alex, wants a divorce, jetting to Florida to visit his wife's ister, Dominica. She owns a motel, they have an affair.

The love triangle is simply a vehicle for Barthelme, though. He's not particularly interested in plot or story, but in scenes, in snapshots which illustrate such fashionable problems as fear of intimacy, loneliness, hostility, and other sub-clinical manifestations of the modern malaise.

Try, for example, this scene early in Tracer. The TV is on, the sound off, Martin narrates: "She told me stories about her marriage. I don't know if it was the matter- of-fact way she told them, or what was in them, or both, but I was terrified. These were horror stories, the kind you read about in the newspaper. I wanted to do something to make her feel better, but there wasn't anything to do but sit and listen. About nine we started to make love but then quit in the middle of things and went for a walk. We got hamburgers at a beach dive called the Rubber Shack that specialized in scuba gear, then w back to the motel. She fell asleep ten minutes into David Letterman."

In fact, Barthelme's characters are too absorbed in their own problems to be sexy. And if sex is talked about in other than euphemistic terms, it is used for the purpose of inflicting pain: Martin's soon-to-be-ex- wife, Alex -- who arrives soon after Martin because, while she doesn't want him, she doesn't want him to have her sister -- tells him about her seduction of their neighborhood grocer.

"'Oh, I wanted to tell you something.' She stopped rearranging the clothes in the suitcase and grinned at me. 'You know the manager in the grocery store at home? The one you always said I wanted to sleep with? Well, you were right.'" He responds by throwing a can of Tab at her, after which follows a scene which could be funny except that it seethes with the sort of hostility only a decayed marriage can produce.

So how did Martin find out that their marriage was falling apart? Martin tells us what he told Dominica: "I told her Alex had turned to me during one of those postcard breaks on MacNeil-Lehrer and said she thought we'd be better off if we just forgot the marriage."

And even though they are having an affair, Martin and Dominica don't interrelate so well, either. When Dominica tells Martin about her ex-husband, Mel, and all the terrible things he's done, Martin watches cable television, switching channels. Yes, intimacy is difficult.

YET JUST WHEN you think Martin is all veneer, he will say something like: "I was lonely too, but all I could think about was what wasn't there any more, which felt awful. I'd lost it. Five years of stuff sucked away, reduced to civility, manners. It wasn't so much what was gone, but what wouldn't be there."

People go places together in Tracer, yet they never seem to be together. They pile into a car to go to P. Rob Turner's cherished Pancake House ("'I feel pretty good about these combos, except the Burger 'N' Bean. Forget that. I can't figure that sucker out, know what I mean?'" says Turner), or to Captain Mike's Oyster Heaven, but they're always talking past each other.

Of course, there's also the matter of brand name consciousness, a familiar component of today's fiction. For Don DeLillo in White Noise, brand names are a mantra ("Dacron, Orlon, Lycra Spandex"), but for Barthelme they are fixtures in the cultural landscape -- Sony Betamax, Pentel, B. Dalton, Mini-Mart, Avis, Tastee-Freeze, Tab. And when Barthelme enlists them in the manufacture of similes he assumes more than familiarity.

Brand names and dissolving marriages are so prominent, and plot and characterizations so unbearably light that Tracer is mostly a novel of manners and gestures and attitudes and nuance, the sort of book from which a cultural anthropologist could quote with impunity to support a thesis about the emptiness of modern life.

There are scenes in Tracer which would sustain someone like Henry James for chapters, but Barthelme slices them off in a page. Yes, this is emotionally freeze-dried and shrink-wrapped fiction which puts on exhibit a world where life has little meaning and there is no exit. This empty world needs a witness, though, and Barthelme is it.