STEPHEN SCHLESINGER honed the skills that-produced Bitter Fruit teaching expository writing to Harvard freshmen. A Law School student at the time. Schlesinger was a third--generation Harvard instructor: his father, Kennedy biographer Arthur Schlesinger, Jr. taught history in the yard, as did his grandfather. Arthur Sr. Anuncle, John K. Fairbank, recently retired from the Faculty. It was "a lot more grueling than I ever imagined." Stephen Schlesinger recalls of his stint grading papers.

After graduation from Law School in 1968, Schlesinger founded a magazine called The New Democrat, a political monthly to the left of the Democratic party. Later, he worked as a speech writer for George McGovern's presidential campaign, wrote a book about that experience, became a staff writer for Time, and took a year of to help Sen. Edward Kennedy '54 (D -Mass.) in his 1980 bid for the Presidency.

As Schlesinger tells it, Bitter Fruit resulted from his interest in the CIA. In 1976, the Agency was being thoroughly investigated by Congress. Schlesinger, a little restless at Time, undertook some research of his own and became intrigued by the constant references to the 1954 coup in Guatemala. "There would be a single sentence in almost every article I read on the CIA about the coup with no further explanation," he says. "So I decided to send away to the government to see what they had."

Under the Freedom of Information Act. Schlesinger applied to the State Department for materials on the events in Guatemala in 1954. Eight months later, he received 1200 pages of documents. They described, on a day-to-day, basis, what the U.S. ambassador had done during the 10 days of the coup. As Schlesinger remembers it. "Reading this factual account of the actions the U.S. took to overthrow a foreign government. I realized I had a potential book on my-hands."

With the help of a close friend. Boston Globe Latin America correspondent Stephen Kinzer. Schlesinger began more detailed research. The authors asked the FBI for information. It took the Bureau two years to comply, and the end result was 500 pages, most of were blanked out for national security reasons. The CIA, the principal actor in the Guatemalan drama, has yet to release any documents to Schlesinger, almost seven years after his initial request.

Today, Schlesinger is pleasantly surprised by the success of Bitter Fruit, now in its third printing. "When we first started the project in 1976, there was little interest in this country for Latin America," he says. "We had trouble finding a publisher, when we did we got almost no advance, and we had to hold down other jobs while we worked on the book."

Schlesinger believes he and Kinzer touched a nerve in America because the Reagan Administration has made an issue of Central America "from day one." And he adds, "when people saw what a mess El Salvador was becoming, they got concerned with the whole region."

The relevance of Bitter Fruit. Schlesinger claims, is "almost cerie." He draws a striking parallel between the Eisenhower Administration and President Reagan's Washington. "It seemed inconceivable to me that a government like Eisenhower's with John Foster Dulles could come back into power in this country," he says. "Then you wake up one day and find Ronald Reagan in the White House and Al Haig as Secretary of State mounting the same polemical statements about communism in Central America as Eisenhower did in 1954."

And the CIA, maintains Schlesinger, is also coming back into vogue. The Agency under director William Casey seems a throwback to "the freewheeling days of the 1950s when the CIA believed it was omnipotent and could shape the destinies of far-away countries. Now with its new power to intervene domestically, God knows what will happen."

The tragedy of the 1954 coup, says Schlesinger, is that left to its own devices. Guatemala would probably now be one of Central America's few democracies. "Some of the CIA people involved in the coup who we talked to look back integrate. Yes, they successfully overthrew a government for their country. But what was the result? Twenty-eight years of military dictatorship. And now, ironically, the threat of a communist takeover is, far more serious than it ever was in the 1950s."