For decades, Cosby was America’s ideal dad. His real life was more complicated. Photograph by Milton H. Greene / Archive Images

A warm summer weekend was just beginning in Salisbury, Maryland, and cars were pulling into the parking lots that surround the Wicomico Civic Center. People had come to see Bill Cosby, who would remind them, that night, that he was “seventy-six and eleven-twelfths years old,” and who surely has neither the time nor the need to do anything he doesn’t want to do. What he does want to do, even now, is comedy: he performs about a hundred times a year, mainly on weekends, following an itinerary that often leads him into what promoters call tertiary markets, where fans are not just happy to be able to see him in person but surprised, too.

The Civic Center arena had been converted for the night into a theatre with about two thousand seats, most of which were full by the time Cosby shuffled onstage, a few minutes past eight. When he began his career, more than fifty years ago, Cosby wore natty suits and narrow ties, but these days his performance attire tends to be casual, often flamboyantly so: T-shirts, sweatpants, sandals, socks. He had been provided a chair and a small side table, and as he settled in he rubbed his knees and looked around. “Well, here I am,” he said. He asked what else the arena was used for. “Rodeo!” someone shouted. “The circus,” someone else said. Cosby brightened. “I remember hearing about the circus as a child,” he said, and then stopped short. When other comics talk about Cosby, they often mention his willingness to pause without filling the silence, certain that the audience trusts him enough to keep listening. When he began again, he was talking about being too poor to go to the circus, which set him off on a twenty-five-minute riff about childhood and poverty and an armchair so rickety that his father had to sit perfectly askew so that it didn’t fall apart.

Cosby has always been an economical but effective physical comedian; people howled as he shifted cautiously in his seat, imitating his father in that chair. But his greatest weapon is his strained and stentorian voice, which is easy to imitate but hard to parody, because Cosby’s bewildered vehemence can scarcely be exaggerated. Often, his jokes come alive only in performance, fuelled more by the telling than by the words. In Salisbury, he reminisced about his wife, Camille, who was nineteen when he married her, in 1964. “She was not who she is today,” he announced, and the audience was laughing already. “She was a nice person.” More laughter, and then applause. “You know what I’m saying. If you are married, then you know the way you look at him.” He imitated a wife’s disapproving appraisal, his face serving as the punch line.

In Cosby’s comedy, he returns endlessly, even obsessively, to this basic plot: the struggle of a man against the woman he has chosen and the children he hasn’t. When “The Cosby Show” made its début, in 1984, he was already one of the most successful comics of his generation, and a television star of long standing. The show made him an American archetype: the personification of fatherhood, a word that was also the title of his best-selling book of observations and advice. When he takes the stage, he remains more than anything an exasperated father. Confronting the cosmic impertinence of a child who moans, “I didn’t ask to be born,” Cosby responds, as always, with fond irritation. “Yes, you did,” he says. “About nine months before you were born, I released about sixty million—you were one of ’em. The idea is, first one to the egg locks the door. The others die.” He pauses to let the laughter subside, then turns accusatory: “You could have hung a left.”

Cosby’s current tour is part of a long comeback. His most recent comedy special, “Bill Cosby: Far from Finished,” was broadcast on Comedy Central last year, and he is at work on a new NBC sitcom, tentatively scheduled for 2015, which would reunite him with Tom Werner, one of the executive producers behind “The Cosby Show.” At the same time, he is living through an extended retrospective celebration. In 2009, he collected the Mark Twain Prize for American Humor, and earlier this year Chris Rock presented him with a lifetime-achievement honor at the American Comedy Awards, calling him “the greatest comedian to ever live.” Now comes “Cosby: His Life and Times” (Simon & Schuster), a biography by Mark Whitaker, the former editor of Newsweek; the book, written with Cosby’s participation, is invaluable but not, of course, impartial. Unlike most of the lions of American comedy, Cosby is known for routines that aim to avoid giving offense, and yet he has proved surprisingly controversial: for decades, he was regularly criticized for being insufficiently attentive to issues affecting black communities; more recently, he has been passionately attentive, transforming into a culture warrior to deliver fierce indictments of what he diagnoses as an African-American social pathology. And, in the years since “The Cosby Show,” a series of revelations and accusations—including allegations of sexual assault—have jolted fans who had grown used to conflating his work and his life.

During Cosby’s nineteen-eighties heyday, though, he seemed untouchable, and younger rivals, especially African-American ones, bristled at his dominance. In the 1987 concert movie “Raw,” Eddie Murphy told a story about Cosby calling him up and urging him to use less profanity in his act, for the sake of his young fans, including Cosby’s own son. Murphy recalled being so offended that he telephoned Richard Pryor, who offered some defiantly un-Cosby-like advice: “The next time the motherfucker calls, tell him I said suck my dick.” Years later, the idea of rebelling against Cosby’s old-fashioned propriety has itself come to seem old-fashioned, making it easier to appreciate his persona as a sustained comic performance, one based on an uneasy tension between fondness and disgust. His virtuosity endures, even as his age begins to dictate not just the content of his comedy but its form.

In Salisbury, Cosby held forth for two hours, without notes or an intermission, and at times he seemed to forget what he was talking about, only to recover with a joke designed to make it impossible for the audience to pity him. As he was sprawled on the stage, during an absurd explanation of how to fend off a bear attack, his face went blank. “Um, this is embarrassing,” he said. “Because I really don’t know how I got down here.” People laughed and cheered, trying to figure out whether this was part of the act. “I don’t know why I started talking about the bear,” he said, and then he became once more an exasperated father. “I mean, I know why: to save your lives.” He frowned. “But why would I care enough?”

In 1962, the Times introduced its readers to a Temple University student who was spending his summer telling jokes at the Gaslight Café, the prototypical hipster coffeehouse, on Macdougal Street. The headline was “Comic Turns Quips Into Tuition,” and the story portrayed Cosby as an accomplished athlete and a low-key provocateur: “a young Negro comic who is working his way through college by hurling verbal spears at the relations between whites and Negroes.” What followed was a warm tribute to an unknown performer of “considerable promise,” but Cosby wasn’t flattered. “He had opened up to the reporter, tried to show him how thoughtful he was, and he was pigeonholed as another angry Negro comic,” Whitaker writes. (The article had mentioned jokes about the Ku Klux Klan, neighborhood integration, and the first Negro President.) In the months that followed his appearance in the Times, Cosby began to reinvent himself, scrapping riffs on current events and instead describing for audiences a childhood that sounded more easeful than his own.