ONE OF THE MOST heartening attributes of contemporary science fiction is its diversity of approach, style and subject matter. I refer to written rather than cinematic sf. These four books give folks who are finicky about their assisted daydreams a dandy excuse to forgo that bag of oversalted popcorn and that lumpy theater seat in favor of a reading lamp and a secluded easy chair.

John Crowley's Engine Summer (Doubleday, $7.95; Bantam paperback, $1.95) presents a depopulated, far-future America where crumbling interstates and brontosaurian shopping malls testify to both the might and the folly of their makers. Rush that Speaks, a member of the isolated Little Belaire community of truthful speakers, sets out from his forest home to "find all our things that are lost, and bring them back." Like all meaningful quests, this one has a psychological dimension, which Crowley illuminates with uncommon sensitivity and grace.

Nowadays sf and fantasy quests are as numerous and annoying as gnats on an August lake shore. Amid this swirl of formulaic mediorcity Engine Summer is a strikingly original and involving book.

So accomodate the lovely idea that Rush that Speaks is recording his hagiography on pieces of eight-sided glass, Crowley calls the subsections of his novel "facets" and its four major divisions "crystals." Because Rush wishes to become a "saint" -- that is, to live a "transparent life" worthy of many retellings -- the structural strategy of Engine Summer is made to reflect (pun altogether appropriate) its thematicontent. Indeed, Crowely's ending suggests a circular storytelling pattern that is simultaneously rejuvenating and imprisioning for Rush that Speaks, and we are both moved and horrified by his predicament. Its author's third novel, Engine Summer is as rare and welcome as those brief out-of-season respites so gently and humorously evoked by its title.

"The universe has a dark corner, the human soul, which is its reflection." This pigquant epigram appears in "Space for Reflection" in Brian Aldiss' New Arrivals, Old Encounters (Harper & Row, $9.95), a collection of 12 stories. Although it might have been lifted from one of the more somber facets of Crowley's book, what this observation most tellingly reflects is Aldiss' desire to cast light -- through the medium of succinct and heartfelt narratives -- on our species' dogged metaphysical yearnings. With wit, humor and sheer storytelling skill, then, Aldiss explores first causes, ultimate ends and man's search for meaning in an indifferent universe.

As a result, at least nine of these 12 stories provide a kind of interrsonating commentary on one another. In "The Small Stones of Tu Fu," almost a teaching parable, God commemorates the life and thought of an 8th-century Chinese sage, while in the space opera "Non-Isotropic" Aldiss puts forward the now fashionable notion that consciousness, like hydrogen, is one of the basic building bricks of the universe. My favorite in this collection, however, is "indifference," which expands this last notion into a starting but completely credible metaphysical system called Theomanity. Aldiss' tales are often novels in miniature, packed with intellectual as well as emotional substance, and I recommend them unreservedly.

By contrast, Jack Dann, a young writer still honing his skills, often ignores the loftier spiritual aspirations of humanity to descend again and again into the nightmare terrain of the subconscious. The dust jacket of Timetipping (Doubleday, $8.95), his first collection, is festooned with eulogistic comments by several well-known sf writers, one of whom compares Dann to Roald Dahl, Franz Kafka and, by criminy, even T. S. Eliot! The wonder is that many of these stories actually deliver the goods, albeit with a staccato, knife-edged prose and a purposely disorienting passion that corroborate Barry Malzberg's avowal that Dann is a genuine original.

Two stores in Timetipping -- "The Dybbuk Dolls" and "camps" -- are absolutely first-rate. I might note in passing that the the deliberate sundering of cause from effect in a few of these stores produces a seemingly arbitrary succession of images that, although admirable in execution, may lead a first-time reader to surface from the page for both air and light. "The Dybbuk Dolls," however, compellingly creates an entire horrific world by yoking its phantasmagoric imagery to a coherent storyline. "Camps," meanwhile, combines traditional narrative values with dream imagery and temporal shifts to make a poignant statement about the Holocaust.

Despite the perfection of these last two stories, the novella "Junction" is both the cornerstone of this collection and the best introduction to Dann's method. Like several of Aldiss' stories, it posits the idea that consciousness is an irreducible attribute of the universe. Says one character, "The only thing of value you have to bequeath the world is your consciousness; only consciousness will survive matter and time." But instead of erecting an all-encompassing metaphysical system on this idea, Dann goes spelunking through the private consciousness of Ned Wheeler, his protagonist. Wheeler's own odyssey unravels on the muddled interface between waking reality and nightmare, culminating in the apparent surrender of his consciousness to Ahasuerus, the Wandering Jew. Wow.

The Wandering Jew gives way to Satan in Walter Tevis' new novel Mockingbird (Doubleday, $10), another crafty exploitation of Judeo-Christian archetypes. Robert Spofforth is "a Make Nine robot, the most sophisticated piece of equipment ever to be fashioned by human ingenuity." In the artificially grown body of a powerful black man he possesses all of the recorded knowledge and some of the haunting residual memories of a dead engineer named Paisley. Virtual dictator of a depopulated, far-future America (although the setting really has little else in common with that of Engine Summer), Spofforth wants only to die but cannot countermand the programming that prohibits his suicide. Here, then, is a character potentially larger than life, dystopia's answer to Milton's Satan.

For better or worse, however, Tevis chooses to make Mockingbird not so much Spofforth's story as that of the lovers Paul Bentley and Mary Lou Borne, who defy the manifold repressive dicta of the state -- "Don't ask, relax," "Quick sex is best," "When in doubt, forget it" -- first by learning to read and then by conceiving a child. They are Adam and Eve to Spofforth's Lucifer, an angel paradoxically incapable of falling until Paul and Mary Lou have succumbed to the temptation of forbidden knowledge and returned in triumph to grant him his death wish.

Doubleday is touting Mockingbird as a literary benchmark comparable to Huxley's Brave New World or Orwell's 1984. Although I found the novel thoroughly engrossing, this well-intentioned publicity push overstates its credentials as a pathfinder or groundbreaker. No matter. I suspect that because of its affirmation of such persistent human values as curiosity, courage and compassion, along with its undeniable narrative power, Mockingbird will become one of those books that coming generations will periodically rediscover with wonder and delight. If it violates dystopian convention, it does so by concluding with -- well, an upbeat dying fall.

Let me conclude with a final crotchety observation. Tevis' previous novels -- The Hustler and The Man Who Fell to Earth -- were made into noteworthy films. Mockingbird will probably follow them to the screen. If it does, I fear -- although I hope otherwise -- that it will succeed less well as film than it does as novel. For Paul Bentley's sake, then, preserve that secluded easy chair and hang on to that invaluable reading lamp. In the written word reside both challenge and solace, and more than a modicum of our humanity.