The publishing firm of Harcourt Brace Jovanovich, one of the most venerable in the business, is soon to make a guinea pig of itself. Before the year is out it will put directly to the test the momentous question: Is it possible to publish books without the life-support system provided by Elaine's, the Four Seasons and the University Club?

Yes, the Big Apple has been cored once again. For a variety of reasons, most of which seem to boil down to money, Harcourt Brace Jovanovich is leaving New York. Its trade-book division, which for a number of years has been run from offices at Third Avenue and 47th Street, in the heart of Publishers' Row, by Labor Day will be moved to San Diego. Yes, San Diego.

It should be understood that trade publishing is a relatively small pea within the big pod that is HBJ. The company, a member of the Fortune 500, is a major publisher of textbooks and professional books; it is also big on leisure, with three marine parks -- including Sea World in Orlando, Fla. -- and a string of fast-food eateries, and it owns valuable real estate in various locations. In the corporate scheme of things, Virginia Woolf and Gu nter Grass doubtless swing a good deal less weight than sharks and dolphins.

But within the hermetic little world of trade publishing, HBJ is a formidable presence; its decision to depart New York is thus a major development, and an unsettling one. Though its chairman, William Jovanovich, is regarded in some quarters as the George Steinbrenner of book publishing, it remains that his firm does serious and distinguished work. Its list for the spring of 1982 is as respectable as any in the business and perhaps, in fact, the best of the lot; the authors on it -- with new books and/or reprints -- include Stanislaw Lem, Gu nter Grass, C.S. Lewis, Georges Simenon, Virginia Woolf, Boris Pasternak, T.S. Eliot, Alice Walker, Vladimir Nabokov and Eudora Welty. This is no fly-by-night operation that is heading West.

It is heading there, in the considered opinion of its competitors, to die a certain death. Franklin Rodgers, head of Scribners and Atheneum, told The New York Times that being in Manhattan is essential: "You just do so much business each day with the agents, authors, book clubs and magazines located here." Roger Straus, who runs Farrar, Straus and Giroux, pointed out that "Houghton Mifflin and Little, Brown have managed to remain competitive although based in Boston, but they maintain New York editorial offices, and Boston has a publishing tradition." Straus recalled the collapse of World Publishing in Cleveland: "It folded because it was too far out of the mainstream."

Perhaps so. But a strong case can be made that many of the troubles the book industry confronts are directly attributable to that "mainstream." Book publishing in America operates on the principle that Saul Steinberg was right: The western boundary of the United States is the Hudson River. The offices of almost all the major houses are within a few blocks of each other in midtown Manhattan, and the industry conducts its daily affairs with an incestuousness that, to the outsider, is quite astonishing. Editors, agents, subsidiary-rights directors, publicists, marketing and distribution people -- all move within a world so tiny that a single conventional bomb, detonated at the intersection of Madison Avenue and 48th Street, would wipe out almost all the custodians of our national literature.

Since such drastic action would dispatch many of my most treasured friends to the Great Book Party in the Sky, I cannot, in good conscience, recommend that it be undertaken. But there are times when it is mighty tempting. The book business is a wonderful place, full of energy and excitement and challenge; but it is also, like the city that nurtures it, as hermetic and provincial as the most ingrown small town. What the singer/songwriter Billy Joel calls the "New York State of Mind" certainly can be stimulating; but it also can be narrow and, for a business that attempts to reach out to the entire country, counter-productive.

Not, of course, that the book industry is the sole culprit. So far as I can tell, the only pro basketball and hockey teams that get game tapes on the CBS "Morning" program are the four New York teams; the news magazines, for another example, have recently covered the opening of a new wing at the Metropolitan Museum of Art with a thoroughness surely far out of proportion to the rest of the country's actual interest in it. New York's sense of municipal self-importance is overweening; since the media are based there, the country gets a big bite of it every day. The book business just adds its own little nibble.

But provincialism in publishing is especially flagrant because of the industry's incredible self-absorption. The same people gather in the same places to talk about the same things, day after day after day. They read the same newspapers and magazines, watch the same local news programs, attend the same cultural events. If they leave town, it is to visit the Hamptons or the Vineyard -- where they go to the same parties and sun on the same beaches. They share the same interest in literature and commerce, the same tweedily liberal politics, and the same conviction that what interests them interests everyone else. The result of all this is that they are too often, even if unwittingly, prisoners of the New York state of mind.

In large measure that's because they hardly ever leave New York, except on vacation. Getting a publishing person to visit another part of the country in the pursuit of his or her business is almost impossible. I know of only one editor, though there may be others, who regularly ventures into the hinterlands in search of writers and readers. The rest count on the agents -- who themselves rarely leave New York except to close movie deals in Los Angeles -- to bring the writers to them.

Obviously these are busy people, and they can accomplish a lot more by staying in one place than by flying hither and yon. But they, and the industry, pay for this convenience. The tunnel vision that they develop is reflected in the books they publish. If "everybody" in New York starts talking about something -- the women's movement, EST, the Yankees, Reaganomics -- the one absolute certainty is that a small flood of books devoted to that subject will be published presently. Few of them will make any money, because there will be too many of them. And few of them will be of interest to many people outside the tiny circle in which they were born, because most of the time New York and the nation seem to occupy entirely different planets.

So I for one wish Harcourt the very best of fortune as it heads West. I have enough New York in me to be skeptical about San Diego as a seat of cultural and intellectual activity, but I also have enough of the provinces in me to think that the soft, clean air of southern California may prove salubrious. HBJ may miss out on a few books that "everybody" in New York is talking about, but it may also discover some books that, while beneath the contempt of the Upper West Side, are of value and interest to American readers. If its move is a first step toward the dissolution of New York's near-monopolistic control over what America reads, there could not be better news. But don't hold your breath.