SOMETIMES PARADISE By Judith Green Knopf. 274 pp. $17.95

IN THE second sentence you know where you are: "Splendid even for Palm Beach, the Carristas' palazzo dazzled the mind." And if the mind manages to recuperate from the wonder of the turrets and Byzantine portico, the whole "more lavish now than it had been during the boom-time twenties, when Vanderbilt had commissioned Addison Mizner to build it," there is "the live-horse carousel and the Dom Pe'rignon fountain, where golden faucets spouted chilled champagne."

We are in the Land of the Idle Rich, a country the visiting writer enters in order to harvest sleazy sex and enough brand-name goodies to rival the Neiman-Marcus Christmas catalogue. The harvest, of course, is meant to show the reader the hollowness and folly of a life where "lobsters tumbled over each other like waterfalls, and the oysters were piled into mounds resembling Alpine peaks." Who would choose lasciviousness and lobster over a Big Mac and a pure heart?

We know who, and so does Judith Green, as she produces yet one more formula novel with a poor but innocent heroine triumphing over the wicked world. Loretta Worship has long blonde hair, big blue eyes and rosy cheeks. She also has a miserable childhood spent acting as a shill for her preacher daddy, whose leers for the Lord let you know right away what kind of nastiness he's going to get up to.

But before the reader can get bored with the unrelenting awfulness of Loretta's life, a Greyhound bus whisks her away from the bible belt and she begins the arduous task of making her way in the world. The reader must begin the almost equally arduous task of trying to follow Loretta through a series of elided transitions that scoot our heroine (now learning to be a nurse) from one place to another without bothering to give the reader a change-of-address card.

Do not bother going back to see if you missed the key sentences. I did and you didn't. Just accept that Loretta moves fast and that before you know it she is giving an extremely rich (handsome, old) man a new lease on life. His name is Chukker Dunbar, and after an extravagant European honeymoon, where Dunbar's former mistress takes Loretta in hand and teaches her how to choose lunch, Loretta is ready for the return to Palm Beach.

Palm Beach is the villain of the piece, a place, one woman reflects, where one "often encountered stinging nettles disguised in nosegays and barbed wishes buried beneath smiles." Seeing the beach bums converge on the innocent Loretta, she "felt marrow drain from her bones," because "too many times she'd smelled the flesh and watched the silently screaming victims attempting to escape." And this, mind you, is an Easter lunch. You can imagine the carnage that occurs when Loretta agrees to run the Feather Fantasy, a charity ball.

Loretta is not only innocent; Loretta is good, and she soon abandons her attempt to join the natives in the hootchy Gucci, and sets herself the serious task of bringing integration to the Palm Beach hospital. In this she is aided by Chukker's son Wilson, who, when perplexed, "tugged at his left eyebrow," a mannerism which must have astonished the hard-to-astonish idle rich.

THE WRITING in Sometimes Paradise is terrible, but that is not its worst fault; the popular romantic novel is often full of sentences every bit as bad as this one: "Wilson especially liked watching the old bigots in whose mouths butter would harden unctuously vying for invitations from those they once didn't admit existed." No, the real fault of the novel is slackness. Loretta's goodness never wavers, her success is never in doubt and even the Awful Secret of her past is a little mouse of a thing, hurriedly trapped and thrown out the door by her adoring husband.

Novels of good and evil, no matter how shallowly conceived, succeed because of the tension of the opposing forces. Successful writers of popular novels know enough to make the devil an attractive fellow, offering his sins of the flesh in a way which will titillate -- else where's the virtue in giving them up?

When a novelist fails to create this tension, there is nothing left but to concentrate on the writing. And in books like this, that will never do.

Susan Dooley is a Washington critic and writer.