The most startling and gratifying literary event of recent vintage is the appearance of Gail Godwin's remarkable novel "A Mother and Two Daughters" in the number one position on the current mass-market paperback best-seller list. This is approximately as plausible as the appearance of Earl Wild's recording "The Art of the Transcription" in the number one position on Billboard's Top-40 charts.

The rest of the mass-market list, published in the Feb. 4 issue of Publishers Weekly and yesterday's Washington Post Book World, is pretty much par for the traditional course: Movie and television tie-ins ("A Few Minutes With Andy Rooney," "Sophie's Choice," "The Winds of War"); schlock fiction ("Fever," "Traditions," "Pacific Vortex!"); romances ("The Judas Kiss," "Palomino"); sci-fi ("The Hitchhiker's Guide to the Galaxy," "The Restaurant at the End of the Universe"); philosophy as it is practiced in southern California ("Love," by Leo Buscaglia, PhD). Few surprises there, and little to cheer about--indeed, without the three tie-ins there would be nothing to cheer about.

Yet perched incongruously atop this grab bag of the familiar and the predictable is "A Mother and Two Daughters." On first glance, it simply doesn't belong there: Leading the pack, with nearly 1.3 million copies in print and the pressmen ready to go back any day for more. It is not a flashy novel, or a particularly sexy one; no one is murdered in it, and none of its characters is a thinly disguised version of John Belushi or Marilyn Monroe; it takes place on this planet and in this century; it proceeds at a leisurely pace, with no titillations to hustle the reader along. It is a serious work of (yes) art, quite consciously Victorian in structure and tone, and the gratifications that it offers, though manifold, are for the most part extremely subtle; yet there it sits at the very top of a list in which highest honor is usually paid to the commercial and/or the execrable.

How on earth to explain this? I took the question to an astute friend and a fellow admirer of Godwin's novel. She responded with characteristic alacrity and precision. "It's a book that responds to the concerns of a great many readers," she said. "It's a middle-class novel, and I'm not saying that pejoratively. Most fiction these days is either highly literary or highly commercial. The middle ground--fiction about the lives that most readers of books actually lead--is rarely filled. I think in fact it helps explain why so many British novelists have large followings in America now. They fill a void created by their American counterparts."

My friend was, of course, exactly right. Most buyers of books in this country are members of the middle class, but remarkably few of the books they see in the stores and libraries have anything at all to do with their own lives. Most readers are people of intelligence, education and sophistication, but none of these qualities necessarily makes them sympathetic to or interested in the vast bulk of available new fiction. From the literati they receive, with occasional exceptions, narcissistic contemplations of the tiny terrors of life in the sweatshops of the mind; from the hacks they receive gory romans a clef, sappy romances, cynical "inspiration" and frivolous escape--all of it couched in prose that would, or should, make a high-school sophomore shudder.

That they read any of these books at all is a tribute to their forbearance and, above all, to their unquenched thirst for books. They seem to read some writers (Saul Bellow comes leaping to mind) out of a sense of duty inflicted on them by the literary establishment; others (Sidney Sheldon? Judith Krantz?) presumably are read because they provide reliable if unimaginative entertainment. But how on earth can Bellow's Chicago dons or Krantz's Rodeo Drive nymphos connect with those millions of us who spend our days in the mundane business of raising and dispersing families, paying off mortgages, fretting over taxes and SAT scores, buying groceries and getting the dishwasher fixed?

The answer needs no elaboration: They can't. And so millions of Americans who find satisfaction and diversion in reading have had to make do for some time with a contemporary literature that resolutely fails to discharge a central obligation of literature: to tell us about ourselves, to help us understand our lives and whatever meaning they contain. John Updike writes about the middle class, but his portrayal of it is so contemptuous as to be devoid of validity or pertinence. Peter Taylor writes brilliantly about the middle class, but he is a short-story writer and readers want novels; much the same is true of the comparably brilliant fiction of Eudora Welty, whose finest work is to be found in her short stories. Evan Connell, whose novels about Mr. and Mrs. Bridge are small classics, has long since gone on to other matters. Peter De Vries is a masterful novelist of middle-class manners, but he is more widely regarded (and too often, alas, dismissed) as a humorist.

The field is, if not empty, sparsely occupied. John Irving's "The World According to Garp" is a middle-class novel in its themes and situations, if not its characters and settings, and I think this more than anything else explains its enormous popularity. The same goes for the novels of Anne Tyler, which are peopled with characters whose gyroscopes are slightly skewed but which deal in the most immediate and intimate ways with the ordinary business of getting on with life. Larry Woiwode's "Beyond the Bedroom Wall," though influenced structurally by certain techniques of the avant garde, is at heart a middle-class novel of the old-fashioned kind: populous, expansive, spacious.

In other words, a Victorian novel. As my perceptive friend noted, Jane Austen and Anthony Trollope and William Makepeace Thackeray were "middle-class novelists," as are the British heirs to their tradition who have won so many devoted American readers: Barbara Pym, Elizabeth Jane Howard, Margaret Drabble. Until a couple of decades ago, there was a comparable, if thinner, American tradition. Theodore Dreiser was a middle-class novelist, although he wrote about the lower classes; so were Edith Wharton and Scott Fitzgerald, who wrote about the upper classes. The writer whose work best combined seriousness of purpose with popular success was John P. Marquand, in particular in his novels dealing with middle-class life in World War II. But by 1970, with the death of Marquand's linear descendant John O'Hara, the tradition of the middle-class novel seemed to be exhausted.

Now, though, Gail Godwin has brought it vigorously back to life, and the miracle is that she has found a vast new audience for it. The word of mouth that comes to me about "A Mother and Two Daughters"--and I have heard more of it than about any novel since "Garp"--is that readers are greeting the novel with a joyful sense of rediscovery, a renewed awareness of what fiction can be and what it can do. I can't remember the last time the best-seller list looked so good.