The desk in Robert Caro’s office has a rounded notch, a clean little half circle that lets him snug his wooden chair into his custom-made workstation. Instead of legs, the top rests on a pair of sawhorses. Shims raise the surface to where his elbows naturally rest when Caro’s pen rolls across the white legal pads on which he writes the first drafts of his epic biographies.

The height was calibrated by President John F. Kennedy’s personal physician, Janet G. Travell, M.D., a specialist in back pain whom Caro sought out after hurting himself playing basketball. Travell decided to assess his condition by watching him work. “So she sat on the floor in my office, and she said to me, ‘Do you know you sat at your desk for three hours without moving?'” Caro recalled. “She said, ‘I’ve never seen anyone concentrate like you.'” When he finished The Power Broker: Robert Moses and the Fall of New York (1974), Caro dedicated it to his researcher, Ina, who is also his wife, and to Travell, who made possible all that would follow.

“The most comfortable position in the world is not lying in bed,” Caro says. “It’s sitting at this desk.”

It’s where America’s most honored biographer has spent much of the past five decades, grinding out the first four books of what was conceived as a trilogy, the magisterial The Years of Lyndon Johnson. Now 83, Caro has paused in the work of the final volume to publish Working, a conversational, behind-the-scenes compendium addressing the questions he hears most often, starting with, Why do your books take so long to write? Eight years passed between The Path to Power, the first in the Johnson series, and Means of Ascent (1990), a dozen more before Master of the Senate and another 10 until The Passage of Power, which delivered LBJ to the White House.