Lynn Nesbit

“Obviously, the National Book Award was very gratifying,” Lynn Nesbit said, “but can it possibly make up for the loss?”

The literary agent was reflecting on her client Joan Didion’s memoir, The Year of Magical Thinking. It was, she said, a difficult subject to address.

Ms. Nesbit, 67, has had more than an agent-writer connection to Ms. Didion and her award-winning meditation on death and its effects—she is entwined with the book’s narrative. Ms. Didion’s late husband, John Gregory Dunne, was also a client and friend of Ms. Nesbit. Ms. Nesbit spoke to Dunne twice on the day he died, and the memoir describes how she was the first person to visit Ms. Didion when the author returned from the hospital that night.

“I knew Joan had no family in New York, so I went over,” Ms. Nesbit said.

In her four decades as a literary agent, Ms. Nesbit has cultivated close relationships with writers of widely varying styles and sensibilities. “You have to attend to whoever is in need at the moment,” she said.

Ms. Nesbit’s writers include critical luminaries like Ms. Didion and Tom Wolfe, and commercial juggernauts like Michael Crichton. Currently, she has the No. 1 book on the New York Times best-seller list, Jimmy Carter’s Our Endangered Values. Ms. Nesbit resides in a $3.5 million Park Avenue apartment and has a country house in Connecticut’s Litchfield County.

She came to New York in the fall of 1960, fresh out of Northwestern and the Radcliffe publishing course. After a brief stint reading French manuscripts as an editorial apprentice at Ladies’ Home Journal, she convinced the agent Sterling Lord, whom she’d met at the Radcliffe course, to hire her as an assistant.

“I had an instinctual feeling that this was something I wanted to do,” she said. “I felt it was probably faster-paced, and as an agent you could work in a more independent way than you could in a big publishing company.”

In addition to handling office busywork, Ms. Nesbit assisted Mr. Lord with his magazine writers. Her first clients were Donald Barthelme and Victor Navasky. In 1963, she called Byron Dobell at Esquire and asked him to arrange a meeting with Tom Wolfe, who had just published “The Kandy-Kolored Tangerine-Flake Streamline Baby” in the magazine. She persuaded Mr. Wolfe to sign up with her, even though she was some seven years his junior and had virtually no agenting experience.

“I still don’t know why he ever signed with me,” she said, “I still have to ask him, because I was this kid.”

Mr. Wolfe said Ms. Nesbit saw a chance to do a book where he didn’t see one, suggesting a collection of his magazine work.

“She told me, ‘I have your first book,’” Mr. Wolfe recalled of his first meeting with Ms. Nesbit.

“I thought, ‘Gee who’s going to read a book of magazine pieces by someone who they’ve never heard of?’” Mr. Wolfe said. “In fact, it became a best-seller.”

In 1964, at the suggestion of a friend, she helped establish the literary-agency division of Marvin Josephson Associates, which would become the modern-day ICM. (In late 1988, she left ICM to form a partnership with Mort Janklow, retaining her loyal client base.)

Ms. Nesbit’s next big break came in 1965, when she signed Michael Crichton while he was still in medical school.

“He said, ‘Let’s grow up in the business together,’” Ms. Nesbit said.

Publishing executives who have negotiated deals with her say that she possesses a talent for understanding both the literary and commercial aspects of the business.

“She’s a great reader,” said Jane Friedman, the chief executive of HarperCollins. “She’s got a sensitivity and a nose for what has commercial potential.”

“She’s a very tough negotiator for her authors. But there’s a lot of realism there,” said Jonathan Galassi, the president of Farrar, Straus & Giroux. “She’s very aggressive in a very genteel way.”

Or as Mr. Wolfe put it: “She has a lot more nerve than I do. She establishes the target and goes right for it. She asks for sums I’d never dream of.”

Those sums have reached stratospheric heights. In 2001, she brokered a reported $30 million deal for Mr. Crichton when he moved to HarperCollins after a 30-year run at Knopf.

“I hope I’ve shown you can be tough but honorable,” Ms. Nesbit said. “And I hope I’ve shown you can build a career by developing writers and not stealing them.”