The Hot Ones : MAMista, <i> By Len Deighton (HarperCollins: $21.95; 416 pp.)</i>

In this, his 23rd novel, Len Deighton has deserted his beloved Berlin and the aftermath of the cold war for a putative Marxist revolution in the impoverished but mythical South American country of Spanish Guiana.

Deighton calls this chilling novel of betrayal and deception “MAMista,” which is an acronym for the rebel group, Movimiento de Accion Marxista, whose objective is to depose Spanish Guiana’s ruling despot and replace him with one of its own.

But the backwater revolt is sputtering and wouldn’t provoke much more than an international yawn were it not for its two main resources. The first is its principal cash crop, coca, the essential ingredient of cocaine, and the second is the semi-secret discovery of a pool of oil so vast it almost makes Kuwait seem like a dry hole.

Two rich and powerful forces are concerned, even obsessed, with Spanish Guiana’s political future. In Los Angeles, a cabal of drug barons swears it will maintain a steady flow of coca paste, no matter who rules the small South American country. In Washington, the President and his nefarious advisers are equally determined that Spanish Guiana’s oil, once refined, will be pumped into American gas tanks.

It’s not quite that blatant, of course, because the oil also will serve a higher purpose. As one of the President’s advisers notes, the oil monies could wean Spanish Guiana’s present ruler “away from the drug revenues. It could give him a legitimate revenue. And the oil would give us a lever. He’ll have to lean on the drug growers, or we could turn off the oil-money tap.”

Some might argue that such advice would never be heard in the White House, but Deighton’s fictional President seems no less feckless than were actual Presidents of recent memory. He is vain, petulant, cunning, paranoid, and the only quirk that truly distinguishes him from other White House tenants is that he speaks in complete sentences--most of the time.

Meanwhile, the L.A.-based drug cartel has decided to dispatch a drug baron’s nephew to the MAMistas as an envoy. The nephew is Angel Paz who, despite his name, is a perfervid Marxist, a journeyman bomb-maker and all of 20 years old.

Angel is met at the Spanish Guiana airport by Inez Cassidy, who is 30, beautiful and one of the revolution’s truly committed. She and Angel Paz soon encounter Dr. Ralph Lucas, a 45-year-old medical missionary of sorts, who served with an Australian infantry regiment in Vietnam and, like many a fictional and cinematic veteran of that war, suffers from a “terrible anger and a cynical bitterness that could border on despair.”

Dr. Lucas also is the closest thing to a protagonist the novel offers. But he is, in essence, an anti-hero, albeit an engaging one, and it’s inevitable that he and the beautiful and committed Inez Cassidy fall in love.

The fourth member of the quartet of principal characters is the maximum leader of the MAMistas, known only as Ramon, whom Deighton describes as “the sort of man TV commercials cast as . . . loving husbands who need margarine instead of butter.” Although 40, balding and going to fat, Ramon is a true charismatic, which makes him dangerous not only to his enemies but also to his followers.

Beginning with his first novel, “The Ipcress File,” in the early 1960s, Deighton employed a lively, even bouncy style that he readily admitted owed much to Raymond Chandler. But over the years his style has depended less and less on wisecracks and more and more on astringent observation, cunning plots and dialogue that’s always crisp and sometimes even inspired.

It’s a style of such distinctiveness that, after reading a couple of blind paragraphs (almost any of them will do), you know it’s Deighton’s writing. And if the style has lost some of its happy bounce, it more than makes up for it with acute characterization, sardonic wit and an unfailing eye for the telling detail.

Deighton needs all of these gifts to lead Angel, the bomb-maker; Inez, the committed, and Lucas, the despairing doctor, into the Spanish Guiana jungle and, it is hoped, out again. For it is these three, accompanied by a ragtag band of the MAMista faithful--plus a captured black CIA agent--who hold the fate of the revolution in their increasingly grubby hands.

It’s a long, nasty, hot, stinking trip through the jungle--or tropical rain forest, if you like--where the enemies are not only the pursuers, but also hunger, disease, exhaustion, weather, rivalry and an engulfing bitterness that threatens to turn into despair--just as Dr. Lucas expected all along. There are moments of savagery, valor and even of self-sacrifice, plus enough treachery and betrayal to satisfy even the most rabid fan of duplicity.

“MAMista” is a very good and very sad novel about people, innocent and otherwise, who are sucked down into the mire of international politics and espionage. It can be read either as an exceptionally well-written thriller or as a cautionary tale--or both. For those who do most of their reading in the summer, it’s the perfect book for the beach--especially if it’s raining.