Any reader who traverses the entirety of Theodore Sturgeon’s “Selected Stories,” now published, 15 years after his death, by the prestigious Vintage Books division of Random House, is almost certain to wonder just what happened here, once upon a time. There is greatness, and there is a tragedy. Why is it only now that these stories have come out of the dark? Why wasn’t their author recognized long ago as an innovative and ambitious short story writer, one of the best America has produced? Why do so many of his stories shake themselves apart? Why do some of them tear us apart?

There’s also a mystery here. Sturgeon’s stories — even when astutely selected, as in this volume; even when they’re heartbreakingly fine, as most of these tales are — give off a sense that something terrible must have happened long ago, almost certainly to Sturgeon himself. Which is not to say that Sturgeon was a writer who could not control his talent, or that the work in “Selected Stories” is anything like incompetent. Neither is the case, though some of the tales assembled here seem to run away from their author, and Sturgeon himself was certainly capable of spouting the awfullest flapdoodle, like some inebriated Ancient Mariner, who stoppeth one of three in the airport lounge, and saith, “All you need is love, all you need is love, get me?, all you need is love,” ’til the cows come home.

But most of the “Selected Stories” do not read like that. They are far more dreadful, and more fine, than that. They are like the residues of some terrible accident, one of those mass pileups on the interstate only visible from the CNN helicopter, anguished Edvard Munch faces turned up to the television cameras trying to convey something.

The intensity is shattering, so shattering that some of the tales burn right through the usual conventions of storytelling, and their protagonists — some of them so bound in passion that they are nearly mute — also tend to fall through the fabric of normal life, like the inarticulate hero of “Bianca’s Hands,” whose ultimately demented adoration of the slim beautiful hands of an idiot girl named Bianca leads him to marry her. The end is grotesque, grand guignol, profoundly pathological. We are left with ashes, a sense that someone (the author? the lover?) has been screaming into our skulls.

“Bianca’s Hands” is a tale of horror, a form given over to the imparting of “unnamable” emotional states that give you the vicarious shakes, but most of these stories are science fiction, a genre whose protagonists, during the period Sturgeon wrote most of his work, tended to be gripped not by passion but by some sort of world-changing project. Sturgeon was first and foremost a genre writer. The 13 titles assembled in “Selected Stories,” which constitute a mere 12 percent or so of his output of short fiction, were mostly written between 1944 and 1955, and almost all were published in magazines like Astounding, Galaxy or the Magazine of Fantasy and Science Fiction. Only “It” (1940), an atypical horror tale featuring bad slime gussied up as Swamp Thing, and “Slow Sculpture” (1970) are from outside that central period. One story alone went straight into book form: “Bright Segment,” an overdrawn tale of psychopathology with no genre content, was published for the first time in “Caviar” (1955), a Sturgeon collection.

For most of these stories to get published, therefore, they had to wear sheep’s clothing. They had to look as though they were a natural part of science fiction’s Big Story during those years, when the field was gripped by an extroverted, expansionist dynamic. The Big Story was about heroes who intended to make this world work better or to discover new worlds to conquer. The physical universe was something to manipulate, not to commune with. Love was a reward for good service, not the heart of the matter. Aliens were to be fought if inimical, or domesticated if not; they were not often found to have lessons to impart to us, certainly not soppy lessons about how humans should relate to one another, as in “The Sex Opposite,” where aliens who breed by exchanging cell nuclei, like paramecia, show humans how to really get it together. “The Sex Opposite” is a story that needed some genuine over-the-top sex to cement its message, but — unlike Robert Heinlein a few decades later in “Stranger in a Strange Land,” with its explicit lessons in heterosexual grokking — Sturgeon could not in 1950 come out into the open and clearly say what he wanted to convey: He wanted to tell his readers to love each other, and to have lots of sex while doing so.

But he continued all the same to plow the fields of genre, whether he did so because he couldn’t publish elsewhere or because he loved the feel of speculative fiction, which gave his rampaging talent tools to work with. It is not the fault of that genre that, in the end, those tools — that field, those editors, these readers — cramped a great talent until he became silent; he wrote very few stories after the 1950s. It is not the fault of science fiction that Sturgeon tore himself to bits in its teeth. But he did. And it is our great good luck that his rage to express himself generated so many tales whose emotional rightness pierces through the veils of circumspection, moving us all the more through the upwelling pressure of the almost said. You could almost hear the wail.

It was the wail of a man with universes to say, and no tongue. But fortune really was with us, as most of “Selected Stories” demonstrates. Every once in a while Sturgeon found his tongue — and it happened frequently enough to make up the contents of one big book like this, and probably a couple more. His best stories about sex, like “The Sex Opposite” or “The Skills of Xanadu” — where liberated, seemingly primitive villagers trick a visitor from another planet into carrying back to his totalitarian state the seeds of Sturgeonesque rebellion — are as full of hidden dynamite as those great Hollywood romantic comedies made when literal obedience to the Hayes Code didn’t clear the air of sex but rather charged it with the stuff. (A movie like Howard Hawks’ “Bringing Up Baby,” in which Cary Grant and Katharine Hepburn never actually kiss, is perhaps as erotically charged a film as it’s possible for a viewer to experience without bursting.)

So the emotions were, occasionally, fed into stories that could sustain them. This is perhaps clearest in the climax of “The Widget, the Wadget, and Boff,” which argues with palpable intensity that men and women are unnaturally isolated from one another; that the normal forms of human social interaction are forms of bondage; that when humans open themselves to one another and to the world, it is not just love that they feel, though human beings are only truly human when loving. What they feel is an instinctive equilibrium of joining, a balancing of the entire human species in something like a dance. This is what governs the actions of the alien couple (the Widget and the Wadget, to give them their names) who, disguised as boardinghouse proprietors, test their boarders nearly to destruction by forcing them to be honest about themselves. Honesty, Sturgeon suggests, is almost intolerably difficult for the unaided human to achieve; and absolutely necessary, if we are to gain the universe. And the heart of being honest is to share love, as one of the awakened protagonists eventually understands:

That’s what Bitty and Sam [which is what Widget and Wadget call themselves on Earth] gave us — a synaptic reflex like the equilibrium mechanisms, but bigger — much bigger. A human being is an element in a whole culture, and the culture itself is alive … I suppose the species could be called, as a whole, a living thing.

We may doubt that Sturgeon’s passionate longing to share is the answer, as he thought it was, to all our woes upon this planet, but there is no gainsaying the deep urgency of his plea. Over and above the pleasures of his storytelling — for he could tell a rattling yarn when it suited his deeper needs to do so — it is why he should be read today. These stories, taken together, brief us about species togetherness; they plead to us: Do not shut down. Do not become less than human. Do not become a solitude.

Please, says Sturgeon, staring up at the cameras.

Once upon a time — about a century ago — something happened in the world of books that, for a while, boded no ill. H.G. Wells, Arthur Conan Doyle, P.G. Wodehouse and Edgar Rice Burroughs consciously invented (along with a lot of other writers like Robert Louis Stevenson or Bram Stoker who didn’t have a clue) the kind of story we now think of when we think of popular genres: detective stories, science fiction, horror, superman adventures, etc. These writers, responding to insatiable demands for copy from the sharp editors who ran up-and-coming new magazines, created stories that could be repeated: Sherlock Holmes and Tarzan are nothing if they don’t happen again and again. They created markets, and they created, only half unwittingly, the monster of the Demand for the Same.