MILTON, Mass. In 1997, Janna Malamud Smith, daughter of the writer Bernard Malamud, published a book called "Private Matters" in which she argued for the importance of privacy in a culture of talk shows and tabloid journalism. Human dignity, Ms. Smith wrote, is based on shielding and protecting the deepest parts of the self from scrutiny. Moreover, the most important of human relationships are formed within the carapace of privacy.

So it may come as a surprise to some people that this month, Ms. Smith, 54, is publishing "My Father Is a Book" (Houghton Mifflin), a memoir of her father, the most private of men, in which she reveals not only how deeply autobiographical his novels were, but also the fact that he had an extramarital affair with one of his Bennington College students that began in the early 60's. The Malamud family, which until now has resisted all biographers, has also given the British scholar Philip Davis access to Malamud's extensive papers for a biography to be published by Oxford University Press.

Why has Ms. Smith chosen to break her silence now? "Writing a memoir, you're still in control," she said with a wryness characteristic of her father. Ms. Smith resembles her father, too, with her square jaw and her articulateness. She also wanted to write her book while her mother, Ann de Chiara Malamud, was alive. "I needed her to tell me where I was wrong," she said.

Along with Saul Bellow and Philip Roth, Malamud, who died in 1986, was part of a triumvirate of American Jewish writers who dominated the national literature in the 50's and 60's. Malamud won the Pulitzer Prize and two National Book Awards. In works like "The Assistant," "The Magic Barrel" and "The Fixer," he borrowed from myth and folklore and transformed the stories of ordinary Jewish lives into moral fables.

Unlike Bellow, of whom it was said he wrote a novel about each ex-wife, or Mr. Roth and Claire Bloom, who each wrote books based in part on their bad marriage, Malamud remained married to the same woman all his life and retained the image of a devoted family man.

Ms. Smith, a psychotherapist, explained why it had taken her 20 years to write about her father: "I needed that privacy to figure out who I was. I needed to learn how to write before I wrote about him. I needed some distance."

"One of the struggles as the kid of a famous parent is the huge incentive to become a narcissistic extension of them," she added, "like Athena born out of Zeus' head."

In the book, Ms. Smith describes Malamud as affectionate toward her and her brother, Paul, living a quiet, small-town life in Corvallis, Ore., where he taught from 1949 to 1961 at what was then Oregon State College. Still, Ms. Smith writes, when other fathers were coaching baseball, hers adhered to a rigid writing schedule. Malamud was a gentle figure, but "he was consumed by the question of whether he could realize his talent without becoming ruthless in ways he just couldn't abide."

Malamud's own childhood in Brooklyn was one of terrible impoverishment. His father, Max, was barely literate in English and, to Malamud, often seemed inept in trying to provide for his family in the New World. Malamud's mother, Bertha, and his brother, Eugene, were both mentally ill. Bertha died when Bernard was 15, possibly a suicide. His last memory of her was seeing her waving to him through the barred window of a mental institution. He was not allowed in to visit her. Later, he tried desperately to help Eugene, but without success.

Ms. Smith said that her father was driven by the desire to give his children the opportunities that he had lacked as a child. Paul Malamud, now 58 and a government worker in Washington, said, "We were sort of dubbed the family that was supposed to be better than the first." (Mr. Malamud would not discuss the memoir or living members of his family.)

In 1961, Malamud, by now famous, moved his family to Vermont, where he had taken a job teaching at Bennington College. Into the stable world he had created for himself came a young woman, Arlene.

Ms. Smith pieced together their relationship from copies of the letters between her father and Arlene, which he kept. Arlene gave permission for her to quote from her letters, and even to use her full name, though Ms. Smith declined to do so. Ms. Smith said she did not know how long the relationship remained sexual but that Arlene stayed in her family's life for more than 20 years. She was an aspiring writer and eventually became a doctor and psychoanalyst.

At times, Malamud's letters to Arlene are romantic: "I want your life to be as beautiful, as lovely as you are. I love you. B." But for the most part, they are avuncular, "Congratulations on your National Boards! You have every reason to be proud. What a courageous accomplishment."

Ms. Smith said of the affair, "I chose not to know," though she could feel tension between her parents. She was able to ignore it, "partly because of the rules Bennington gave you to play with." The permissive attitudes there all but encouraged affairs between students and teachers, she said. Indeed, during their years in Bennington, her mother also had an affair. Ms. Smith said she also became aware of that relationship as it was happening. Meanwhile, Ms. Smith said, one of her high school teachers pursued her relentlessly, and her parents did not intervene.

Reached by phone in Cambridge, Mass., Ann Malamud, now 88, acknowledged that both she and her husband had affairs. "Essentially I feel that my husband and I had a very strong bond," she said. "Other relationships sometimes happen in life of various sorts. That does not mean that they destroy everything."

In Malamud's sixth novel, "Dubin's Lives" (1979), about a biographer from Vermont, the married Dubin takes his young girlfriend, Fanny, on a trip to Venice. There, he thinks he catches sight of his daughter with an older man. Dubin justifies his own behavior with the idea that the age difference between his daughter and her lover is even greater than that between him and Fanny.

Ms. Smith said she believed the scene referred to her relationship with her older teacher. At the time the book was published, "I was really, really angry about it," Ms. Smith said, adding, "To have your family life turned into fiction, everything in the service of fiction and not in the service of family."

Yet Ms. Smith, who is married to an English teacher at Milton Academy and the mother of two sons, said she never confronted her father about "Dubin's Lives." "It was a taboo to take on his entitlement to the creative process," she said. "His writing was privileged."

In discussing her father's life with Mr. Davis, his biographer, she said, "We both realized that the man who claimed he was writing fiction tracked his life more closely in the fiction than we thought."

For instance, "The Assistant," Ms. Smith said, though long thought to contain biographical elements, "was much more autobiographical than people know." Morris Bober, the seemingly ineffectual Jewish grocer, becomes a redemptive figure, almost Christlike in his goodness and gentleness, to his assistant, the petty hoodlum Frank. "The book was about how much he was trying to work out his feelings about his father," Ms. Smith said.

"He struggled with his life all the time," she continued. "How to manage what happened with his mother and brother. There were a lot of powerful things he was dealing with."

"He wanted privacy," she said of her father. "One of the functions of writing is to transmute shame. What you present, when you present it, it's your choice. Writing was a way to cloak his shame."