HOW I SAVED THE WORLD. By Philip Slater. Dutton. 337 pp. $16.95.

EARLY IN THIS, sociologist Philip Slater's first work of fiction, former mental patient Taylor Bishop writes a passionate letter to the secretary of defense, warning of the dangers of nuclear escalation. A few weeks later he receives this in reply from the Pentagon: "Thank you for your letter setting out the dangers of nuclear escalation. We here at the Pentagon are very much alive to the perils you have so eloquently described. We appreciate your concern, your anxiety, your sincere desire to dissuade our nation from a course that seems, as you put it, suicidal. But how do you think we feel? Shut up in a huge impersonal office all day with a noisy air conditioner, answering letters from people who think they know more than the department of defense. You talk about destroying the world -- what about unemployment? I have a family to support just like you."

Such is the tone of How I Saved the World, the preposterous but thoroughly engaging store of the disingenuous Taylor's self-chosen mission to avert Armageddon. Taylor's methods are, well, unconventional. In collusion with a group of North American shamans called Makluts, and especially the ornery, powerful Louise, Taylor uses out-of-body travel, automatic writing and dream analysis in his psychic investigation of the government's defense strategies. And what he finds is, well, unconventional. He must not only defuse Project Joshua, a plot to use a concert by the rock band Crushed Nuts to trigger an accidental missile launch, but he must also expose Wyatt Earp, a government-sponsored psychic communication project designed to let the president bypass fail- safe mechanisms if he thinks it's a good idea.

To succeed, Taylor must match powers with the delightfully sinister Delbert Sneath, double agent and alchemist. Taylor is joined in his adventures by a likable bunch of companions, including rock vocalist Polly Morfuss and her unlikely lover Brandon Valdemar, a harmless if somewhat pompous academic. Most endearing is Grace Castleman, Taylor's friend, lover and co-narrator who keeps practical matters under control while Taylor exercises his psychic powers.

It is through Grace, a refreshingly disaffected academic, that Slater, himself a disaffected academic, pokes fun at the academy and at his former colleagues, who here are preoccupied with scholarly triviality as the world spins toward disaster. How I Saved the World is about our precariously balanced nuclear world, but happily Slater seems really to have left the podium far behind; he makes his point not by lecturing but by telling an outrageous and thoroughly enjoyable modern-day adventure story. BE BURIED IN THE RAIN. By Barbara Michaels. Atheneum. 241 pp. $13.95.

WHEN Julie Newcomb, a medical student, agrees to her mother's request that she spend the summer tending to her invalid 85-year-old grandmother, Martha, she does so reluctantly. Doing so means putting up with a lot more than the sticky Tidewater weather and uncomfortable accommodations of the decrepit Carr mansion. It means putting up with cousin Matt Carr, a smooth small-time Virginia politician with big-time ambitions. It means putting up with the narrow religiosity of Joe Danner, the intrusiveness of the psychic Polly Hornbeak, and other local products of this cultural backwater.

And though she doesn't know it, it also means meeting up again with former lover Alan Petranek, a self-centered archaeologist who would like nothing better than to dig up Maidenwood in its entirety. But worst of all, it means dealing with Martha Carr, the tyrannical mistress of Maidenwood, and with a groundswell of repressed memories linked to a horrific childhood spent at her mercy. There are skeletons and excavations of more than one variety in Be Buried in the Rain. While some dig for clues to confirm the myths about Maidenwood, others would like nothing better than to keep old bones out of sight. At the bottom of Julie's psychological dig lies the one clue that will explain both the local scandal and the Carr family's unhappy history. Barbara Michaels is deft at mixing local history and myth with a plot of gothic dimension, and her many fans will once gain be very glad. PARGETERS. By Norah Lofts. Doubleday. 333 pp. $16.95.

IN Pargeters, Norah Lofts attempts to do for the English civil war what Gone with the Wind did for the American. And much as Margaret Mitchell used the Tara plantation as a central symbol of sweeping historical change, so Lofts uses Pargeters, a war-torn Suffolk manor house named after the pargeter, or plasterer, who gave the house its distinctive trimwork.

Pargeters is the story of Sarah Woodley-Mercer, who through the untimely deaths of her father (plague), mother (freak accident), and older brother (war casualty) becomes the mistress of three farms, including Pargeters, and of her struggles to keep household intact and business afloat through two decades of civil and domestic strife: during the war itself, when her laborers are recruited into Cromwell's army and she is forced to sell off property to support the Royalist cause, and following King Charles' execution, when Pargeters is sequestered for redistribution to Parliamentarian supporters. In all this she is joined by a large cast of characters who reside at Pargeters, including a cruel and tight-fisted Puritan husband, whom she endures for convenience, and various others whose lives have been disrupted by the war.

Unfortunately, these character are so hastily drawn and killed off so fast (there is a lot of dying here, including suicide and patricide) that it is difficult to feel loss for any of them. Even Sarah, the enduring heroine, is without human dimension. This is Lofts' final book (she died in 1983), and it would be nice to report that she went out in style; unhappily, she did not. Pargeters is a book for only the most uncritical Lofts fans, those who like history in broad strokes and are ready to forgive clumsy plotting and overdrawn prose. KARAN. By B. Wongar. Dodd, Mead. 248 pp. $16.95.

IN 1984, THE Australian government established a royal commission to investigate the consequences of nuclear testing that was done secretly by the British in the tribal lands of South Australia during the 1950s and 1960s. The commission concluded that the testing, which lasted about 10 years, had destroyed portions of aboriginal culture.

In Karan, B. Wongar has taken this piece of history and transformed it into a sad and mysterious work of fiction. It is the story of the Rev. Anawari Mallee, an aborigine by birth who was seized from his tribe as an infant, educated in Europe, and returned to the Australian hinterland in a position of relative privilege. Although his title is meaningless, it has certain benefits, including a house in town, a white fianc,ee and a job at the Tribal Research and Assimilation Centre, which is tracking down radiated tribesmen for what (Anawari gradually learns) is a diabolical brand of genetic research. With access to the TRAC's seemingly omniscient computer, Anawari begins to piece together the monstrous plot and his own part in it, and ultimately he flees into the "green smear" of his tribal homeland to seek his long-lost karan, or tribal soul. This is not a hopeful book.

The pseudonymous B. Wongar, the son of an aboriginal mother and European father and, like Anawari, educated in Europe, sees the clash between tribal values and European civilization and technology as devastating and inescapable. Anawari's flight takes on surreal dimensions as his white pursuers draw on impossibly powerful machines to track and capture him; when he is finally convicted by a computerized kangaroo court, Anawari's realization and B. Wongar's are the same: "Anawari could see, now, that no single human being could be called to account for the blunders of the past -- for the conflict between white race and black was between two entirely separate entities, so different in all but a common desire for existence that destruction of one or the other was inevitable." Despite his wonderfully lyrical voice, B. Wongar's is an utterly despairing vision. THE SECRET GENERATIONS. By John Gardner. Putnam's. 383 pp. $17.95.

BY REVEALING that Giles Railton, ultimate English patriot, master spy and central character of The Secret Generations is actually a communist sympathizer and traitor, I hope to spare you the sense of betrayal I felt when confronted, after long and tedious reading, with this improbable twist. Then again, any conclusion, even one that is totally inconsistent with the facts before it, is welcome relief from John Gardner's ponderous prose and flat characterization. The idea here seems to have been to meld two popular genres, the multi-generational family saga and the espionage thriller, but fans of either genre are likely to be disappointed. Readers of spy stories are used to intrigue and suspense, which they will not find here; and fans of the family saga will expect at least a measure of psychological complexity where none exists. Which is too bad, because the historical event that Gardner has chosen to explore in this novel -- the emergence and growth of foreign intelligence services between 1909 and 1918 -- is intriguing and would seem to provide ideal territory for an exploration of such human qualities as patriotism, bravery and suspicion. Someone ought to work this material into a good novel.