When Deirdre Bair called Nan Talese, her editor, to say she wanted to write a biography of Al Capone, the response was not encouraging: “You’re a literary biographer, and he’s a gangster!” Talese’s reaction was understandable: Bair has cranked out five award-winning biographies—Samuel Beckett (1978), for which she won the 1981 National Book Award for Paperback Biography; Simone de Beauvoir (1991); Anaïs Nin (1995); Jung (2003); and Saul Steinberg (2012). Simone de Beauvoir and Jung were finalists for the Los Angeles Times Book Prize; her biographies of Beauvoir, Nin, and Steinberg were chosen by the New York Times as Best Books of the Year; and Jung won a Gradiva Award from the National Association for the Advancement of Psychoanalysis.

Nevertheless, Bair was already on the Capone trail. It all started, she says, with a call from her friend Jane Denning, current president of the Women’s National Book Association and professor at the Pace University Masters in Publishing program. According to Bair, “her brother, an attorney, had a client named Capone who was curious about his ancestry—he had heard that his father or one of his father’s brothers could have been the illegitimate son of Al Capone.” Bair adds, “They thought the best way to track that would be to find someone to write a book—and could I help her find someone? I asked her what kind of book they wanted: ghostwritten, or as told to? So she put me in touch with him.”

At the time, Bair was not familiar with Al Capone beyond the stories that made him legendary, such as the Valentine’s Day Massacre. After a conference call with some Capones in Chicago and an in-person meeting with about 30 of them, Bair realized “they didn’t know anything about their history. So I did some research, but I found so much contradictory information that the next thing I knew, I was calling Jane and saying, ‘Don’t look any further—I’ll do it!’ ”

Talese ultimately relented, and the biography, Al Capone: His Life, Legacy, and Legend, pubs in October. In it, Bair presents a cultural study of the Brooklyn-born son of poor Italian immigrant parents, a man who became Chicago’s mob boss and American history’s most notorious gangster. Bair had the complete cooperation of Capone’s family, who granted her exclusive access to their personal stories and documents—but only on one condition: that she never reveal their names. “I do not like to use anonymous sources, but I had to do it for this book; they didn’t want people to know where they live or what they do. ‘We’ll tell you everything,’ they said, ‘but you cannot use our names.’ I would meet Branch A, who didn’t know the children of their uncles. They’d become so deeply hidden and private that I became the facilitator to put them in touch with each other! It’s amazing—the fourth generation thinks, ‘That was my ancestor—how cool!’ while their parents and grandparents are ashamed. All Capone’s brothers except Ralph had changed their names.”

In Prohibition-era Chicago, Capone headed a multimillion-dollar gambling, alcohol-bootlegging, and prostitution operation known as the Outfit, whose long-running war with rival gangs resulted in 1929’s infamous Valentine’s Day Massacre. Yet Capone was never arrested for any of that criminal activity; the only charge brought against him was federal income tax evasion, for which, in 1931, he was sentenced to an 11-year term in Alcatraz. By the time he was released, six and a half years later, Prohibition was over, the country was well into the Great Depression, and Capone was dying from neurosyphilis. He lived his final years in Miami with his family.

Intrigued that Alphonse Capone is still a part of everyday conversation, Bair wrote an article in April for the Daily Beast titled “How Did Al Capone Become the New Hitler?” in which she commented that “what is surprising are the frequent references that align the flamboyant Trump and some of the other candidates with Al Capone [as opposed to Hitler and other political figures], the legendary gangster who has been dead since 1947.”

It took Bair only four years to write Capone, as compared with six or seven years for the previous biographies she had written, mainly because there were so few written records. “They didn’t exchange letters. There were no diaries. Only his wife, Mae, kept letters—but in her last years, she burned them. There were no Italian documents. But I was able to pinpoint information from New York City due to the census records. And I am trained in investigative journalism, so I did a great deal of newspaper research in the Chicago newspapers. At the time, there were about 10 or 12 newspapers there, with multiple editions. When you have all that space to fill, sometimes you make it up! I compared all the articles and found that if 10 reporters covered something, there were 10 different versions! So in a lot of instances, I relied on family memory.”

Another Capone complexity that Bair discovered was that “he wasn’t only a vicious, cold-blooded killer; he was really a loving father, and totally in love with his wife while having one mistress after another. And he was only 25 when he took over the running of the Outfit, and his crime reign was six years at the most.”

Al Capone was a first-generation Italian-American, and Bair herself is fourth-generation, so she identifies with him in this regard. “My father was Italian-American; my mother’s family was from Hungary. Both sides of my family came before Ellis Island was set up. My great-grandmother came as a widow and brought her three sons and daughter; one of the three sons was my grandfather, and he determined that his children would be educated. My brother and sister and I identify with our Italian heritage, and the culture in our household was, we saw education as the way to move forward in life. Privately, I consider it a tragedy that Al Capone didn’t have the opportunity to succeed in a legitimate business, because he was brilliant. At the time, [the attitude in New York City] was, as one official put it, ‘We need to keep bringing these Italians in, because the Irish won’t do our dirty work anymore.’ So there were not many opportunities for Capone at the time.”

As a result, the path taken by Capone and other immigrants of the era was highly entrepreneurial; Bair was fascinated to learn that the Harvard Business School, in one of its courses on managerial capitalism, used as a case study the Outfit and how Al Capone ran it.

After each book is finished, Bair has said that she suffers from postpartum depression, which is eased only by having an idea of the next project. In this case, she’s working on what she calls “a kind of writer’s memoir: I knew Simone de Beauvoir and Samuel Beckett while I wrote their biographies, so this will be a book about the writing of the book. I’ll talk about all those encounters and how I interpreted them, as they happened to me. I think enough time has passed.”

As for how her biographies are received, Bair notes, “I strive for as much objectivity as I can. I try to keep myself out of it. Some reviewers have said, ‘The wonderful thing is, you have no idea what she thinks of the person,’ and others were upset at me for that very reason. But that’s what I’m going for. I think the book that needed to be written about Al Capone was not a retelling of the public life, but a story of the private life. Eighty years after his death, this is the story that should be told.”