Here, for those interested in such masochistic undertakings, is a delightfully undidactic, often humorous and always stimulating guide to biographical writing.

On a series of Monday nights in the winter of 1985, at the New York Public Library, six authors of outstanding biographies talked about the joys, pitfalls and puzzles of their craft. This book, unobtrusively edited and introduced by William Zinsser, reproduces what they had to say.

Robert Caro described his efforts to separate the real Lyndon Johnson from the legendary one so painstakingly fostered by Johnson himself. Ronald Steel recalled his discovery, while writing of Walter Lippmann, that facts do not "exist in any significant way . . . that reality is not about facts but about the relationship of facts to one another."

"At home, hanging above my writing desk," Paul Nagel told his audience, "are pictures of ten women, each of whom appears in the biography of the women in the Adams family I'm preparing now. I often look up at Abigail, Louisa, Abby or one of the others. Their presences, with their gazes upon me a century or more after their time, are moving reminders that the severest requirement imposed on the biographer is humility. Writing about another person's life is an awesome task, so one must proceed with gentleness born from knowing that the subject and the author share the frailties of human mortality."

David McCullough, gathering material on Harry Truman, learned early in the process that to grasp his subject he must "know the territory." He must "go to the place," to Jackson County, Mo., where Truman lived for 70 of his almost 90 years. There McCullough listened hard to those who, knowing Truman before he came into the limelight, saw the flower in the bud. "It's much more important to listen when you're interviewing people," he decided, "than to worry about what questions you're going to ask. Beginners in this kind of work often make the mistake of going in with a list of questions. Pretty soon the person interviewed feels that he's filling out a questionnaire. And something happens -- it isn't conversation."

Jean Strouse, writing of Alice James, William and Henry's invalid sister, voiced the belief that "modern biography operates at the intersections of public and private experience" and that it must look for the actual, as distinct from the avowed, wellsprings of human behavior.

And Richard Sewall, dealing with Emily Dickinson, found himself coping with a problem of structure. Dickinson had no public experience. She sat in her house in Amherst, writing poems and letters and talking to herself, the outer course of her days unruffled and all the tumult of her life within her. How, Sewall asked himself, did one make "the story of a life that had no story?" How did one get at the inner tumult?

He tried first what he called the "genetic . . . approach." He gathered and synthesized the literary influences that seem to have gone into the making of the poems, only to find that method didn't work. At this point Henry James came to his rescue, "James's notion of reflectors -- how, in a work of fiction . . . the central figure . . . is defined, not only by what he does and says . . . but by his relations with" the other people in the story. Sewall began examining the people who mattered to Emily, hoping to find mirrored in them bits and pieces of Emily herself. He began with a grandfather and came down the line, with the result that in his "Life of Emily Dickinson" Emily isn't born until the first chapter of the second volume.

One opens a multiauthored work, anticipating some unevenness in the vitality of the prose. But I detected no lapses in this one. "Extraordinary Lives" is a lively book, likely to interest not only biography writers but also other students of what Tennyson called "the abysmal depths of personality."

The reviewer is the author of "The Biographer's Craft."