WHY would 7,000 booksellers from all over the country leave home on the first big holiday weekend of the season to spend four days getting sore feet in a cold and foggy San Francisco? To attend the annual convention of the American Booksellers Association, where 17,000 people swarmed around the wares of more than 700 exhibitors. Under the white vault of the Moscone Center 1500 booths, trying to catch the eye with everything from Viking helmets to antique cars, displayed hundreds of books to be published in the months ahead. The booksellers came to gaze, to be courted by the publishers and -- maybe -- to place orders. The Business of Bookselling

ACCORDING to Dee Rogers of Kingwood, Texas, the convention "inspires me to carry on for another year." Not many independent booksellers are laughing all the way to the bank these days, but "I just can't afford to miss the convention," says Jeff Imbach, down from Calgary, Alberta, for the weekend.

Tom Peters of A Passion for Excellence fame was on hand to give some hard-nosed advice to small business folk like Rogers and Imbach. "Discounting is death to the independent bookseller," he said firmly to a capacity audience in one of the many panels that accompanied the convention. He went on to compare bookselling to the clothing business, raising a few eyebrows. His point was that the advent of huge department store chains had overstandardized the clothing industry but, as a reaction to mass merchandizing, a highly successful boutique industry was spawned offering offbeat styles and personal service. The big bookstore chains are having just such an effect on bookselling, says Peters, and he sees a place for both chains and independents. He even claimed that a small store he knew had drivena B. Dalton's across the street to close -- although he declined to identify the location in deference to William Edwards of Dalton's, who was next to him on the platform!

The startling decrease in the amount of computer products and software on display at this year's convention reinforced Peters' message that the specialty of bookstores should be books. Whether it should also be book-related videos seems still to be an open question. Several publishers were displaying videos, including the venerable Alfred A. Knopf. Under the logo of Knopf VideoBooks, their booth featured a six video-cassette set of The Way to Cook, by Julia Child. The cassettes are indeed accompanied by a "specially designed booklet" and are described as having a "first printing" of 25,000 copies, but only time will tell when a book is not a book. (At $29.95 The Way to Cook is at least the financial equivalent of a coffee table book.) Reading Is Fundamental

THE THEME of the convention this year was literacy or rather the threat of illiteracy. "Toward a Reading Society," proclaimed the marquee in front of Moscone, and a 20-page special section of the trade journal Publishers Weekly circulating at the convention was devoted to "The Blight of Illiteracy."

In an impassioned and moving speech at breakfast Sunday morning to an SRO crowd of booksellers, Jonathan Kozol (author of Illiterate America) upstaged even Geraldine Ferraro, promoting her autobiography Ferraro: My Story (to be published by Bantam this fall), and Father Andrew Greeley of racy novel fame. (His memoir, Confessions of a Parish Priest, will be published by Simon and Schuster.) Kozol was, of course, preaching to the converted as he reminded his audience that four out of 10 residents of his native Boston cannot read the Boston Globe. Illiteracy, Kozol said, is a threat to democracy -- illiterates seldom vote -- and costs the United States around $120 billion a year in lost productivity. He didn't say how that mind-boggling figure was calculated, but booksellers don't need statistics to tell them that illiterates don't buy books. They were clearly moved on both ideological and practical grounds and gave Kozol a standing ovation. Favorites in the Fall Stakes

GARRISON KEILLOR, tall, rumpled and besweatered ("I knew he'd look like that" commented one passing bookseller) seemed to be everywhere. Viking is publishing his Lake Wobegon Days this fall. The Newman Communications booth prominently displayed a four-cassette set produced by Listen for Pleasure entitled "Listen to the News from Lake Wobegon" with a tape for each season. A best seller for them at $34.95, they said. Keillor was also the star attraction at the closing banquet Tuesday night.

Mary Lou Retton constantly reenacted her Olympic gold medal triumph on video at the McGraw-Hill booth. She was also around in person promoting her book. Creating an Olympic Champion, coauthored by Retton and her coach Bela Karolyi, is written "with" John Powers, crowding the jacket with three names, but then someone has to be in charge of words.

Sequels are always popular and Anne Rice (Interview with the Vampire) with The Vampire Lestat and Rona Jaffe (The Class Reunion) with After the Reunion know they have fans out there waiting for the next installment. Jean Auel has another entry in her Stone-Age saga, The Mammoth Hunters.

British royalty can't lose either and Ralph G. Martin, author of Jennie has an upcoming dual biography of Charles and Diana coming from Putnam. It should have a blank page in the back for additional family.

A new novel from James Michener, Texas, brings smiles to booksellers' faces, as does Jackie Collins with her novel Lucky. Kurt Vonnegut, Joseph Wambaugh and Carl Sagan are entering the lists again, the last with a book on Halley's Comet and his first foray into fiction, appropriately entitled Cosmos. On the Fringe

SENSITIVE party goers at an elegant gathering hosted by the Sierra Club in the Steinhart Aquarium wondered if the finny onlookers would be offended by the hors d'oeuvres served: seviche. . . . A Warner Brothers movie version of Alice Walker's The Color Purple, a nationwide best seller in both hard and soft cover will begin shooting in June. Whoopi Goldberg has been cast as the lead and Steven Spielberg will direct. No wonder the folks at Harcourt Brace, Walker's publishers, are aflutter. Devout Walker fans could also visit at Wild Trees Press, her own new publishing house, which as well as "publishing only what we love" sells notecards featuring eight different views of Walker and family . . . . Macmillan publisher Hillel Black hosted a dinner for former White House chef and Macmillan author, Rene Verdon (Monsieur Verdon did the cooking). Black has just signed that writer of many colors George Plimpton for a "six figure" sum to write a novel featuring the mythic 158-mph pitcher Sidd Finch, who made his debut last April 1. Look for his reappearance in the spring of '86. . . . North Point Press threw a party on the good ship Balclutha. So many came to drink champagne and meet star author Evan Connell, whose Son of the Morning Star gave the press its first best seller, that some North Pointers wondered if they and their guests might all go to the bottom. . . . Far-out hype award goes to the Couch Potato crowd, who picketed outside the convention with signs reading "More Channels, Fewer Books," and "Turn On, Tune In, Veg Out" all to promote their book The Couch Potato Guide to Life: Better Living Through Television. "Only in California," muttered a bookseller from Maine.