NEW YORK, JUNE 14 -- The rumor flashing through the publishing industry this afternoon was so startling that several top executives assumed it must be a joke. But it was true: After 33 years at Simon and Schuster, and 15 as its CEO, Richard Snyder had suddenly been fired.

Snyder, known as both a brutal boss and a brilliant publisher, had built Simon and Schuster into the powerhouse it is today. The firm had revenues of less than $40 million when he took the corporate helm in 1979 and has diversified into a multi-tentacled $2 billion-a-year business. And it has been having a good year, industry sources say, with numerous hardcover and paperback bestsellers.

Jonathan Newcomb, Simon and Schuster's president and chief operating officer since January 1991, will take Snyder's place. Though he has been responsible for day-to-day publishing operations, Newcomb is largely an unknown quantity to the editors and agents who were burning up the phone lines today.

"It was boom -- out of the blue," said literary agent Morton Janklow, a friend and longtime associate of Snyder's. "I haven't spoken to one person in the business who knows what this is about, who even has an acceptable theory."

Actually a number of theories were circulating. Simon and Schuster is a division of Paramount Communications, which was acquired by the entertainment conglomerate Viacom in March after a bruising takeover duel. It was Viacom's CEO, Frank Biondi, who walked into Snyder's office about noon today, Snyder told associates, and fired him.

There has been speculation that Viacom might sell the publishing house to reduce its debt, and that the presence of Snyder, 61, would have proved an impediment. But Viacom's press release announcing the transition made a point of pooh-poohing the sales rumors.

The other, more prosaic, theory postulated a personality clash between the acquirers and the acquired. "It was a difference in styles and philosophy," a source familiar with the decision said. "It was not a single event. ... Dick just has a different style and philosophy about running a big business."

In the aftermath, publishing insiders recalled a New York Times story about the takeover battle in which Viacom Chairman Sumner Redstone was asked whether he knew the high-profile Snyder. Redstone's hesitation and his eventual lukewarm response -- "I think I've met him" -- was widely noted in the gossipy book business. "Snyder had sort of fallen below their threshold," an executive at another publishing house recalled today. "It made people think that Simon and Schuster was a very big deal to New York but didn't register very much with the acquirers."

Viacom will pay the four remaining years of Snyder's contract. It offered him a consultancy, which he declined; he has told associates he wants to be free to seek other opportunities in publishing. Friends have hypothesized that should Viacom spin off S&S, Snyder would try to raise the money to buy it.

Redstone himself, in the bland Viacom press release announcing Snyder's dismissal and Newcomb's succession, called Snyder "a major contributor" to S&S and notes that he "leaves the company well positioned for the future." Snyder was not talking to the press today, except perhaps to Bob Woodward of The Washington Post, an S&S author. "I got a sense of someone going through life reassessment," Woodward said.

Snyder is not a widely beloved figure. In 1984, Fortune named him one of "the country's toughest bosses," jokingly comparing him to the Ayatollah Khomeini. (Snyder had more hostages.) One publishing executive today recalled the many people Snyder himself had fired, using a room that came to be known around S&S as "the executive departure lounge." But even those who dislike him credit him with smarts, vision and a phenomenal track record. S&S had been a modest trade publisher, sold by its founders to Gulf & Western for $11 million in 1975. Snyder led the company as it acquired Prentice-Hall, moved into electronic and business publishing, and added audio and CD-ROM units. He had recently completed the absorption of Macmillan and Scribner's, which S&S purchased in 1993.

"He professionalized what was sort of a loopy business," Janklow said. "It was a business run by professorial types. He wanted it to be profitable. ... He ran a creative enterprise with real discipline."

"In the minds of most people in publishing, he's been synonymous with Simon and Schuster as long as anyone can remember," said another industry insider.

Newcomb, on the other hand, is not well known. "No one thinks of him as a publishing person; they think of him as a finance guy," said the insider. It is telling that neither Janklow (whose S&S-published clients include David McCullough, Jackie Collins and Garry Wills) nor his equally high-powered partner, Lynn Nesbit, has had any dealings with the new CEO.

Rumors that S&S Consumer Group President Jack Romanos would move up to serve as Newcomb's second-in-command were branded as just that -- rumors -- by Viacom.

"I don't have the traditional editorial pedigree," Newcomb, 48, acknowledged in a brief phone interview this evening. He spent 14 years at McGraw-Hill, becoming president of its Financial and Economic Information Unit, before joining Simon and Schuster in 1988. His educational background -- bachelor's in economics from Dartmouth, master's in finance from Columbia -- is also a fiscal one.

But Newcomb said, "Publishing is a large and complex industry today. ... There's a different skills set needed to run a $2 billion business."