FOR MOST of the 60 years of its existence as a commercial enterprise, science fiction has survived as a hothouse genre on the fringe of the big city of literature, for good and for all. Certainly, within its protective cladding, some highly unusual talents have blossomed, talents that might well have come to grief in the stonier soil outdoors. The late Theodore Sturgeon, for one, eccentric and flamboyant, passionate and twee, flourished for nearly half a century within the genre, where for many years before his death in 1985 he had ranked as a top tutelary guru or Old Master for readers and writers alike; but he was virtually unknown to the world at large.

His last novel, Godbody (Donald I. Fine, $14.95), now posthumously published, may show why. On the outskirts of a small American town appears a strange man. He is totaly undressed. He tells the minister he meets on the road that his name is Godbody. Though Christ is never invoked directly, it is perfectly clear that Sturgeon intends his readers to understand that Godbody is Christ come again; it soon becomes clear as well that this is the week of His Passion.

For Godbody, God is love as experienced through the laying on of hands, through ecstatic communion in tongues, and most importantly through sex. How His embodiment of these convictions intersects through one long Friday with the deeper structure of the Passion makes for a story of disastrous simplicity. Through the eyes of the minister, his wife, the sexually frustrated sadist Hobo Wellen, a beautiful Swedish artist named Britt, the insanely prurient town tyrant Willa Mayhew, and a few others, Godbody is seen in his transcendent nudity; his clear-cut ever-ready sexuality; and eventually Willa Mayhew shoots him, screaming shrilly. "This really is a hell of a way to make a living," Godbody tells the disciples, and dies again.

Right from the Procter & Gamble name He takes for Himself, much of Godbody is therefore an embarrassment, and it may be the case that Sturgeon held back from publishing the book himself because he knew that he had got the tone wrong, and that his contemporary fable fatuously simplified the original Passion. "The sun," Britt informs us at one point, "was gone from the tulips, but the way they looked, they remembered it. I lay down and Godbody lay next to me . . . I said part of the sun was still in the tulips; did he think the sun would miss it?" This wallowing pulpy eupepsia, both hectoring and spineless, always marked Sturgeon's worst moments in the hothouse of the genre. He would not have gotten away with it outdoors. Inside, in the 1940s and '50s, telling tales for lonely adolescents, writing of love and sex in the debased language they (and the editors) demanded, he went over the top, vitiated his talent, and wrote in his last years the fumbled epiphanies of Godbody.

But yet. But yet. As Stephen Donaldson says in his afterword, the book comes through. It is emotionally naked, urgent, quite frequently eloquent with the desire to convey the loving gravity of its message: That we must love one another; that our flesh is love. It may be enough to say that through a swamp of bathos he carried his precious gospel; and passed it on. Robert Silverberg BEYOND THE SAFE ZONE (Donald I. Fine, $17.95) announces itself as "Collected Short Fiction" of Robert Silverberg, and it is certainly the case that its 472 fat pages contain a large number of very fine stories, most of the best that the amazingly productive Silverberg has written since he began becoming an Old Master in 1954, somewhere in his late teens. But not all of them are there, by any means. Beyond the Safe Zone is actually an assembly of the best stories Silverberg wrote from 1968 to 1974. But not all of them. "Sundance" is missing, and the award-winning "Passengers," and several others. Of the stories collected here, only "Ishmael in Love" did not originally appear in Unfamiliar Territory (1973), The Feast of St. Dionysus (1975) or Capricorn Games (1976). These three Silverberg books make up Beyond the Safe Zone, which is therefore an omnibus, and a superb one at that; but its publishers should have admitted the fact.

In a rather distanced introduction, Silverberg makes the fair claim that these tales are deeply representative of the troubled, dizzied, anomie-ridden times in which they were written, but goes on to imply, rather less plausibly, that they also share the message of the late William Faulkner in his Nobel Prize gown: that humanity will endure, and even prevail. Through most of Beyond the Safe Zone, this brand of humanism lie buried deeper than cryptoanalysis sounds, and would more appropriately gloss the serene complexity of the stories published in The Conglomeroid Cocktail Party of 1984, the volume that marked Silverberg's welcome return to short fiction. In the 27 stories now recollected, the serenity -- the cool professional polish -- the dynaflow savoir-faire are all a matter of surface presentation.

Beneath lies the pit. Generally we are in the near future, just before the turn of the century. It is a deeply permissive world; technology is permissive, and sex is, and money is available to most of the stories' protagonists though it is rarely mentioned. Psychic powers are often enhanced, and permit body-changing, teleporting, mind-reading, a constant vertiginous interpenetration of self and self, self and time, self and space. There are alternate universes, alternate time-zones, alternate bodies to inhabit. Nothing is impossible, but nothing can be desired with a clean hard passion, either. It is a nightmare of the world of 1970, a nightmare we have become accustomed to, not one we have outgrown. At heart, Silverberg's best stories are parables of adulthood in an adult world -- in other words, a world in which everything can be done, everything can be used, but nothing remains wondrous.

Several of the finest stories, like "The Feast of St. Dionysus" and "Trips" and "Capcicorn Games", explore avenues into the eye of the storm, where something approaching Oneness or God may possibly breathe the universe in and out. But none of Silverbeg's protagonists is a child (where all of Sturgeon's are) and nirvana always slips from their grasp, the demands of selfhood call them back into the world. And the dizzy glut of anomie begins again. For a book of such high savagery, Beyond the Safe Zone is, all the same, a delight to read. Each new story solves a new technical problem; almost all of them dazzle and perplex and reward the reader. It becomes almost intoxicating to despair. James Tiptree, Jr. SINCE the late 1960s, Alice B. Sheldon, almost always writing as James Tiptree Jr., has published her intricate and humane stories in science fiction magazines, collecting them now and again in paperback collections that have gone unnoticed outside her home market. This is to everyone's loss, and it is a pleasure to note that Arkham House, beginning with Tales of the Quintana Roo (Arkham House, $11.95), is about to launch upon a massive reprinting in hardback of her earlier work. The three Quintana Roo stories can serve as a modest appetizer for that feast.

It is, unfortunately, the case that Tales has all the flavor of Tiptree but little of the meat, little of the tightrope-walking complexity of her more extended work, where one plot is never enough, nor one climax, nor one neat message. Generally, Tiptree is a writer of fiery acumen, psychologically acute, sharply compassionate. In Tales of the Quintana Roo, all set on the Caribbean side of the Yucatan Peninsula of Mexico, and all narrated by a protagonist who is clearly herself, this acumen and edge fade into a perfectly respectable -- but slightly cloying -- earnest piety. Her love for the area does come amply across, as do her ecological fears for its survival now that roads penetrate and gringoes surfboard its remotest reaches; but she has chosen to couch these concerns through three didactic fables in which the supernatural aura of the Quintana Roo raises warning ghosts and signals to the world above. The book is nakedly decent but mediocre as art. Compare the stories "Beyond the Dead Reef" with "The Last Flight of Doctor Ain" (1969), and see the difference between immortal art and sermonizing. And be glad, for that great story will soon be with us again. Kate Wilhelm AFTER a couple dozen novels, Kate Wilhelm does very little wrong, though sometimes she seems to lack the energy to be searingly right. Huysman's Pets (Bluejay Books, $15.95) demonstrates the case. In a sort of rehash of the thematic material of the very fine Where Late the Sweet Birds Sang (1976), we get a glimpse of the formation of a group of youngsters with whose genes the awful Dr. Huysman has tampered, making them into a clone-like gestalt whose paranormal powers will soon (it is hinted) rule the world.

In the meantime, Drew Lancaster, a wittily iconoclastic writer who is very deftly drawn, finds something ominous in the sequence of coincidences that draws him and certain others close and closer to the late Dr. Huysman's legacy -- a rotten doctor, a suspicious hospital, some very strange children. The plot is complicated and crafty, and it is only when we are well into the book that we discover that its plot is a plot, that the children have engineered everything that happens so as to effect their escape from confinement. This they successfully do, and the novel ends. It is competent, funny, realistic and sharp; but it contents itself with far too little. We end where it might have been exhilirating to have begun. John Clute is the book review editor of Foundation and associate editor of "The Science Fiction Encyclopedia."