Environmental Case : BIODEGRADABLE SOAP, <i> By Amy Ephron (Houghton Mifflin: $18.95; 159 pp.)</i>

“Biodegradable Soap” is Amy Ephron’s third novel, and third novel set in Los Angeles. Her characters are Hollywood people, with car phones and hot tubs; some of them hunger for movie deals and the beatitude that money and stardom bring. But this isn’t a Hollywood novel so much as an American one.

This also is a warmer novel than Ephron’s last, “Bruised Fruit,” although she carries on in the same spare, compact style, understanding the infidelity, murder attempts and self-indulgence mingled with political correctness that figure in the story. Together, style and substance make for an easy, entertaining read, with a lot of action and intrigue compressed into a fairly small number of pages.

Claudia Weiss is the beleaguered heroine, the mother of two little girls. One day, without any explanation, her husband David moves out. The story is immediately carried to Claudia’s friends by Billy Thomas, an exercise instructor who prefers to be called a personal trainer, thank you very much.

David wastes little time before he takes up with a gorgeous and self-absorbed Italian movie star, Lara Agnelli. Claudia knows it’s serious when David, an agent, explains that he passed on an opportunity to represent Lara, because “it would complicate things.”

Claudia has larger concerns as well. Even before David leaves her, she becomes obsessed with saving the planet from environmental destruction. She attends meetings. She recycles. She starts a scrapbook of newspaper articles that document the poisoning of the sea and the dumping of toxic waste. She makes a list of foods and household items she is supposed to give up, but agonizes over bananas, because they are the favorite food of one of her daughters.

Her struggles recall the obsessiveness of another Hollywood casualty, Maria Wyeth of “Play It as It Lays.” But, as the saying goes, just because you’re paranoid doesn’t mean they’re not really out to get you. In this case, although David and Claudia’s friends think that she is overreacting, we are willing to agree with her that she’s the one having the rational response.

After all, as she reminds us, in the words of a Native American chief: “We don’t inherit this earth from our ancestors, we borrow it from our grandchildren.”

It’s equally true that Claudia’s worry about the environment is a way to avoid thinking about her impending divorce, which is chugging along in lawyers’ offices. Claudia is somewhat resigned: “Probably (David) would be rich, anyway. After he married Lara Agnelli . . . it was something (their daughters) would get used to when they were sixteen or seventeen after they had given Lara Agnelli a really hard time for years.”

In fact, almost all of Claudia’s thoughts about her separation focus on the effect it may be having on her children. She worries about their health, and feels guilty that they get only one parent at a time.

Meanwhile, Billy Thomas, the gossip-mongering personal trainer, gets involved in a scandal of his own: He’s caught in bed with a client, Jacqui Richards, by Jacqui’s husband, who promptly shoots Billy in the foot. Claiming loss of livelihood, Billy files a lawsuit, though perhaps he should count himself lucky at the cuckold’s aim.

These telling, humorous vignettes of upscale Los Angeles life abound: David rents a house from an out-of-town actress, and when it rains, the roof nearly caves in on him, metaphorically enough. The roofer who comes out to fix it is a moonlighter whose real profession is that of clown.

Then there’s Jacqui Richards, the unfaithful wife who lavishes the love that women usually save for their children on her own body. She’s as shallow as the California reservoirs, but even she is pained by the sight of homeless women with their belongings in shopping carts.

And, appropriately, it is David’s broken car phone that finally severs the link between him and Lara Agnelli.

In “Biodegradable Soap,” though, we don’t laugh because these people are different from us. What’s striking instead is how normal, even how square (but in a nice way) Claudia and David and most of their circle seem.

Claudia and David were also the names of a couple in a popular series of novels written by Rose Franken in the 1930s and ‘40s. That Claudia and David were white and middle-class, lived in the East, and their concerns, with a slightly soap-opera-ish bent, focused on marriage and children. The word “recycle” did not appear.

This Claudia and David are white and essentially middle-class, too, but they are older, live in the West, and are connected to the movies (the earlier Claudia wanted to act on the stage). Although on the brink of divorce, they, too, ultimately are bound together by their children.

Thus they are the new emblematic American family. They may not be “typical” any more than Ozzie and Harriet, or Alex and Donna Stone, or the Andersons were, but they represent something we aspire to, in spite of their sometime unhappiness.

Even Claudia’s fumbling environmentalism inspires us, because we relate to it at some level. She can’t quite give up the Hefty bags, but she’s trying , and she expresses a common dilemma when, reading about a woman in Pasadena who grows her own food and rides a bike, she suspects that “the woman’s children were already grown and that she had nowhere that she had to be.”

Ephron shows us a side of Hollywood that, in spite of the foibles of its residents, is neither glamour capital nor desert of alienation. It’s about real people, and that’s refreshing to read.