In the beginning was the Word of Mouth.

"It was during the Jean Harris trial," says ABC-TV correspondent Lynn Sherr. "We were waiting for the verdict, and spending a lot of time just sitting around -- several dozen representatives of the most prestigious news organs in the country, there in a corner of the lobby, all piled on each other."

As the hours passed and the tedium thickened, Sherr remained visibly engrossed in what she was reading, an advance "reader's copy" of a soon-to-be-published espionage thriller by a minor author. When her restless colleagues asked what it was, Sherr recalls, "I must have said three dozen times, 'It's called "Gorky Park" and it's published by Random House and it's great.'"

Afterwards, Sherr called her friend Carol Schneider, publicity director at Random House, and said, "I think I have done a wonderful thing for you."

A few weeks later, "Gorky Park" topped off the best-seller lists and Martin Cruz Smith was a hard-cover household word. Hearing Voices

Before the ad campaign, before the talk shows, even before the printed page, there is Word of Mouth, perhaps the strongest sales organ in the body politic and certainly the least expensive.

It is as integral as ink to the book business. Thousands of titles hit the racks every year, and getting special attention for a single one is like whistling in a hurricane. So publishers with a hot property reach immediately for their Big Mouth lists.

That is: a protean roster of prominent people who put the quo in status and the dicta in obiter, whose luncheon musings or cocktail-hour verdicts can change the shape of the season. Three or four months before a book's publication, these literary log rollers receive either paperhound uncorrected galleys or, later, slik-cover "reader's copies," and the big mouthing begins.

Mailing lists differ from book to book, depending on subject and genre, and range in number from 200 to 2,000 (as for "Gorky Park"), depending on dollar investment and expected popularity. But generally, there is a triad of word-of-mouth weapons in the integrated battlefield of publishing.

The first is getting pre-publication quotes from name-brand authors. Among the most desirable: Kurt Vonegut, Gloria Steinem, John Updike, Erica Jong, Joan Didion, John Gregory Dunne, Dan Greenberg, John Gardner, Woody Allen, Joseph Heller, Gay Talese and Thomas Pynchon, many of whom are consequently knee deep in new novels and scarely know where to begin reading. "I stopped giving quotes," says Nora Ephorn, "because the number of books you really want to give quotes to is outnumbered six to one by books like your veterinarian's new volume on how to feed your cat. If you don't give him a quote, then God help you next time your cat is sick." Nonetheless, she is adamantly pro-mouth: "I believe that what makes books sell, more than anything else, is word of mouth."

Phase two involves a number of institutional Big Mouths, leading literary indicators like Barbara Bannon of Publisher's Weekly and B. Dalton's Kay Sexton, whose weekly newsletter goes to all 540 stores in the chain and hundreds of people in the industry; columnists such as Hilary Mills and Leonore Fleischer; heads of the major book clubs; book-buyers for the large chains; editors empowered to buy excerpts for such supermarket showcases as Ladies' Home Jounral. Redbook, Woman's Day, Playboy, Penthouse, Family Circle and McCall's; talk show hosts and agents of every kind; and scouts for the screen. And then there are opinion-shapers like Steve Rubin of Writers Bloc and Emily Boxer, book coordinator of NBC's "Today" show. Says Stuart Applebaum of Bantam Books, "People use these early warnings as evidence that somebody besides the publisher believes in the book."

Meanwhile, everybody in the business is constantly reading everyone else's material. "When a book comes along that people really love," says Wendy Nicnolson, publicist for Summit Books, a division of Simon & Schuster, "lots of things start to happen -- for example, people start Xeroxing manuscripts and sending them to friends." The rule is: If you've bought it, flaunt it. Galleys shuttle between houses, and soon a big book has a big following even at competing companies. "Publishing is incestuous," says Rubin, and big-mouthing "has much more clout within the industry."

Finally, each publicist and editor also has a mental list of friends, associates and special-interest readers. For example, Random House's Schneider regularly sends readers' copies to such industry outsiders as Bill Kenly, a public relations officer with Paramount Pictures, and Herb Hellman, who works in corporate public affairs for RCA records. "Herb lunches the way I lunch," she says.

"He'll say, 'I just read a terrific book last night.' You also include whoever you know who goes to a lot of parties, who because of business or celebrity sees a lot of people."

And, of course, there are ad-hoc speciality lists: Ralph Lauren was the target of an advance copy of Crown's "How to Make Love to a Man," which publicity director Nancy Cahan also sent to Calvin Klein and photographers Francesco Scavullo and Richard Avedon. Nicholson bombarded the feminist community with early copies of Summit's "The Women's Room."

As the word turns, the only cardinal rule is that each Big Mouth really believe in the book. "You have to have credibility," says Rodney Pelter, book seller-turned-agent and a notoriously effective Big Mouth. "You never go out on a limb for a friend, an author or a publisher -- you only do it for a book." Up and Coming

Right now, the conversational drums are beating for a number of coming summer and fall titles: Colette Dowling's "The Cinderella Complex" (Summit) about why women fear independence; Joyce Carol Oates' Washington thriller called "Angel of Light"; and the new John Irving novel, "Hotel New Hampshire," both from Dutton; Thomas "Black Sunday" Harris' new chiller, "Red Dragon," for Putnam's; Addison/Wesley's "Theory Z: How American Business Can Meet the Japanese Challenge," by William Ouchi; Simon & Schuster's "Mr. American," a novel by George M. Fraser; Colleen "Thorn Birds" McCullough's "An Indecent Obsession" from Harper & Row; "Baby Love," from Knopf by Joyce Maynard, who caused a stir in the early '70s with "Looking Back"; and Crown's "Traditions," the big upcoming show-biz novel by Alan Ebert with Janice Rotchstein.

The genteel jawboning doesn't always work. Anne Tolstoi Wallach's new novel, "Women's Work" -- a sort of "Scruples Goes to Madison Avenue" about a female advertising honcha's fight for recognition -- looked like a big-mouth bonanza after New American Library paid $850,000 for it at auction, hustled it at this year's ABA and sent out 2,000 galleys to a list that included leading woman executives such as Sherry Lansing, Barbara Walters and Gloria Vanderbilt. But the August release is already meeting some resistance from the major mouths in New York (despite favorable early notices in the trade press) and the prognosis is uncertain.

Similarly, a few years ago, despite a hard sell on the salon circuit, Random House's "Kramer vs. Kramer' proved a hard-cover disappointment. Yet the movie became a national phenomenon. And screen success, too, can be the result of Big Mouths in motion. The Triple Play

Four years ago, just before William Diehl's Atlanta-based thriller, "Sharky's Machine," came out at Delacorte, "I was invited to a dinner as a Big Mouth," recalls free-lance publicist Betsy Nolan, who had worked on the book and was a personal friend of Biehl's. "I picked up a pre-publication copy and sent it to Sidney Sheldon, a client of mine. I am very circumspect about sending works to authors, unless it's something that I'm absolutely willing to stake my reputation on." She was, and Sheldon ("The Other Side of Midnight") got the book at his Los Angeles home.

Meanwhile, Diehl's attorney, Irving Kaler, had sent a copy to Edwin Spivia, director of the George film office, who in turn sent it to producer-director-star Burt Reynolds. At the same time, Reynolds' friend Tommy Culla, who reads books for potential film projects, had also sent him a copy. One night after Sheldon and Reynolds had appeared on the same talk show, Reynolds went to Sheldon's house. There on the coffee table was the ubiquitous "Sharky's Machine." "That's the third time today I've seen that book," Reynolds said. "Somebody's trying to tell me something."

Maybe so: Reynolds just finished shooting the film version of "Sharky's Machine" in Atlanta. The Talk of the Town

Depending on the strength of the book and the reputation of its advocate, it can take as few as one or two people to get the town talking. Robert Gottlieb, editor-in-chief at Knopf (and the man who helped get "Catch-22" off the ground in the mid-'60s), didn't have to go the extra mile for Jacobo Timerman's "Prisoner Without a Name, ycell Without a Number." It was only a few blocks to the New Yorker offices, where he gave a manuscript copy to editor William Shawn. The excerpt appeared, and the book was off.

Agent Rodney Pleter, a former owner of the Madison Avenue Bookstore ("the most glittering list of customers any bookstore ever had"), developed big-mouth clout on the strength of his taste and his volume, which sometimes accounted for 10 percent of the hard-cover sales on a single book. He claims to have out-promoted the publishers on more than one occasion. In the case of Hugh Trevor-Roper's "The Hermit of Peking," he stunned Knopf by single-handedly ordering 700 copies and making the title an East yside shibboleth.That kind of customer charisma, he says, takes years to achieve: "You give a book to a Brooke Astor, a Paul Mellon or somebody, and say, 'I want you to buy this book, and if you don't like it, I'll take it back.' And after a while, it's anything you want."

Pelter was also an early and strong supporter of Gael Greene's steamy 1977 novel "Blue Skies, No Candy." After reading the galleys, he says, "I realized that there wasn't a good, trashy, sexy novel -- by a personality who would get out and promote it -- on anybody else's list that season.

"I called [an executive] at Morrow and told him, 'You've got a hot book on your list. Do something about it.' I was met wiht dead silence. So when I went to the American Booksellers Association convention, I told every buyer I knew that there as only one really trashy book of the season. After the book took off, I called Howard Kaminsky [president of Warner Books, the paperback publisher of "Blue Skies"] and he said, 'Glad to know you -- you mae the Gael Greene book for us.'" Kaminsky does not remember the conversation, but does recall the word-of-mouth impact of the Warner cover. The image of a woman's hand upzipping the fly on a pair of obviously male jeans was a lubricious hit, and Warner used it for display cards on the New York subway. "Then a priest and a couple of his parishioners saw it," Kaminisky says, "and took offense and ripped a few of them down. Finally, they convinced the transit authority to have the cards removed. We got a lot of publicity out of that." Getting the Ball Rolling

Sometimes it takes an outright oral attack. That's the conclusion Nancy Cahan, publicity director at Crown, came to when faced with promoting "Princess Daisy" by Judith Krantz. "Judy got sick, and I had to think of some way to get people talking about this book, since I knew we weren't going to do terrific in the reviews." She decided "to get it linked up with a charity. I did some investigating, and came up with Lighthouse for the Blind" in New York. After lengthy negotiations with leadings socialities ("they have the money to buy books and the time to read"), Cahan got the desired result: Last April at the Plaza, the Lighthouse held a Princess Daisy Ball with all the attendant attention in social columns, the fashion press and television.

Cahan did not stop there. Fifteen hundred specially bound and numbered copies of "Princess Daisy" went out to a select big-mouth list. "It had tissue paper on it," recalls one veteran publicist how received a copy. "I thought I was getting a Bible or something."

Cahan likes "planting items" with columnists and generating news stories about books before they are published. The technique worked well with "The Spike," by journalists Arnaud de Borchgrave and Robert Moss, although Cahan also sent out almost 2,000 pre-publication copies (no inconsiderable investment -- at nearly $4 each, bound galleys or readers' copies cost about twice asmuch to produce as finished books) and worked the authors themselves pretty hard. "They had a lot of friends in high places, and we had lots of cocktail parties all over the country," especially in Washington, where she invited "Alexander Haig and the top defense and political people, not so much press as opinion-makers."

In a few months, Crown will publish Moss' first solo novel, a thriller called "Death Beam." The original working title was "Death Star," and when Cahan managed to get it into New York magazine's Intelligencer column, representatives of producer George "Star Wars" Lucas wrote to complaint hat the words "Death Star" were their property. A legal liability, but an asset for Cahan. "I got up a press release about how Robert Moss was ready to take on the KGB, but not Carth Vader. It was picked up in The Times, on cable TV, Leonore Fleischer ran part of the letter, and then Shirley Eder did it." The Garp Gambit

No amount of talk can compensate for genuine literary excitement, however, and no book in the coming months is going to match the liveliest kliterary lobbying in recent memory, the oral orgy that accompanied John Irving's "The World According to Garp." When the manuscript came in to Dutton in 1977, jaws started dropping from day one. The excitement over a major book always begins at home ("You can't fake it," says Kaminsky, "but if you can get people in your own house hot, it radiates out"). kWith "Garp," it began when Jan Rosenman, assistant to the late Henry Robbins, wrote a rousing in-house memo. Then Robbins -- who enjoyed enormous respect in the literary world -- sent a heartfelt endorsement letter accompanying the 1,500 readers' copies. "It worked like it was supposed to," says Lois Shapiro. Dutton's publicity chief, and soon ears were bending up and down the East Coast.

Even the incorrigible Pelter got a piece of the pre-publication action. "I called Henry [Robbins] and said, 'Waht have you got? I'm home sick and I need something good.' He said, 'Have I got a book for you!' I read it straight through, called him back and said, 'This is the greatest book I've read since "Catcher in the Rye."'" Pelter's endorsement, which went out with the Dutton salesmen, said: "Booksellers who don't stock 'Garp' are going to miss the biggest book of the season."

Those how didn't did.