"Most people like to talk about themselves - once you get to them," says Peter Wyden, who likes to talk about himself. "That's all you need to know to become an investigative reporter. Of course, you also have to wear out a lot of shoe leather."

Wyden, 55, proprietor of the publishing house that bears his name, went through several pairs of shoes in the last four years. And now the resulting book, "Bay of Pigs: The Untold Story," is making waves in the military and intelligence establishments.

One reason is his irreverent style: Wyden calls the Bay of Pigs "Waterloo staged by the Marx Brothers." Another is that his subtitle is largely accurate: Until his book, the story of the American-sponsored 1961 invasion of Cuba had large gaps in it.

According to one expert on the Bay of Pigs, "Wyden has done a superb job of putting together the operators' side of the story - exploring the underlying attitudes and showing how the Bay of Pigs connects with Vietnam and even with Watergate. He has talked to these guys and brilliantly put the story in a new context."

It wasn't easy.

"When I began work on the book, I knew nothing about the Bay of Pigs," Wyden recalls. "Like everybody else, I confused it with the Cuban missile crisis. I was ideally situated in the expertise department."

In fact, except as a wordsmith, he was spectacularly unqualified. The future invasion expert had written what he calls "the most motley collected works of any living author." The most successful (co-authored with Dr. George Bach) was "The Intimate Enemy: How to Fight Fair in Love and Marriage," which has sold a million copies in paperback. The one that reminds him most of the Bay of Pigs was "The Hired Killers," for which he had to interview "people who kill for money - on death row in San Quentin, for example."

The idea for "The Bay of Pigs" began while Wyden, as a publisher, was trying to corral a writer, Dr. Irving Janis, author of a book called "Victims of Groupthink."

"The book had a chapter on the Bay of Pigs," Wyden recalls, "and reading it I was mesmerized - by the psychological manipulation of the Cuban participants and by the whole subject."

But Janis could not write a whole book about the Bay of Pigs, and Wyden began working on the subject himself.

He took the idea to Michael Korda of Simon & Schuster, who was also the editor of Cornelius Ryan's war epics and "Is Paris Burning?"

"Korda invented this genre," says Wyden, "and I went to many publishers, but he was the only one who could accept this book.

cThey laughed when Petie Wyden went off to the revolution. But I've never started anything without finishing it."

From his base in New York and Connecticut (where he maintains two homes), Wyden traveled the United States, Cuba and the Virgin Islands, spending several weeks among Cuban exiles in Miami and searching out civilians who experienced the Bay of Pigs invasion in the thatched-hut village of Gironcito, Cuba.

"It was worth it," he recalls."After a while, you learn to do without sleep, though I have not given up wine, women and song."

After four years of wearing out shoeleather for "Bay of Pigs," the experts were asking Wyden for details - including Richard Bissell, the CIA deputy director - who masterminded the American operation, and Fidel Castro, who directed the Cuban defense from telephone booths in grocery stores.

"I had a six-hour conversation with Castro - and there were no bathroom stops," Wyden recalls. "Everything you have read about Castro's personality is true - but particularly strange things happen when you talk to him about his favorite subject. To Cubans, the Bay of Pigs is Valley Forge, it's Washington Crossing the Delaware - something almost holy.

"Three times during our talk, Castro called out to his cronies who were working nearby and yelled, 'He knows more about it than we do.' I have it on the tape."

"A good portion of the time I was with Castro," Wyden says, "I was being interviewed by him: Where were the ships located? Why didn't they fire? Why did this or that go wrong"

But it was easier to interview Castro than some of the American sources.

"The operation was totally compartmentalized," according to Wyden, "and everybody was using code names - pseudonyms. Then there was a tremendous problem of finding these people after you knew who they were. The CIA wouldn't cooperate at all."

A typical example was Grayston Lynch, who was known as "Gray" in the operation and was the de facto American commander in the field, the first man ashore and the one who gave the Cuban brigade the green light to land. "For two years," says Wyden, "I knew of this man only as 'Gray,' and it was vitally important to talk to him. Then one of the Cuban exiles told me he thought the man's name was 'Grayson,' but he thought it was a last name. I finally tracked him down, but Bissell claims to this day that his presence was unauthorized and he was on a sort of busman's holiday."

Everyone he talked to was "nervous,c Wyden recalls, "even 17 years after the event. Of course, right after the battle, many of the CIA men were in tears - some were vomiting into wastebaskets, and it was a terrible scene."

The road to Cuba began in Germany, where Wyden lived until he was 13. From his childhood in Berlin he remembers the sound of gunfire from street-fighting between Nazis and Communists. He was expelled from public school because he was Jewish and moved to the United States at 13. Studying at the night school of CCNY, he was a bit more than halfway to his degree when World War II ended his academic career.

Returning to Germany in uniform, he became a newspaper editor (in German) under the auspices of the U.S. armed forces. "During the war," he recalls, "I was the editor of what was probably the world's smallest newspaper. It was called the Feldpost, and it was delivered to our faithful subscribers by artillery shell. There were no circulation wars, no renewal problems."

After the war, he edited German language newspapers during the occupation for a while, then returned to newspaper jobs in Wichita and St. Louis, five years in the Washington bureau of Newsweek, editorial positions at the Saturday Evening Post, McCall's and Ladies' Home Journal ("the dame business," he calls it) before becoming a publisher ("a final lemming-plunge which I have lived to regret ever since - it's a dreadful business").

Wyden was divorced several years before he gan work on "Bay of Pigs," and his children were all grown - otherwise, he believes, the book would have wrecked his family life. But now he may be willing to undertake similar projects again.

He quotes, with obvious relish, statement by Michael Korda: "The mantle of Cornelius Ryan is waiting to be filled," and then he adds his own comment, only half-joking:

"What can I say? Have mantle, will travel."* CAPTION: Picture 1, President Kennedy accepting flag from Bay of Pigs survivors; Picture 2, Peter Wyden, by Harry Naltchayan