In 1942, New Yorker writer Joseph Mitchell profiled an eccentric named Joe Gould. In it, Mitchell revealed that Gould, a Harvard-educated Greenwich Village bohemian, was writing a magnum opus – something that had never been done – a nine-million word Oral History of Our Time that would be the longest book ever written. Twenty-two years later, the New Yorker published another profile Mitchell wrote about Gould, this one titled “Joe Gould’s Secret.” It explained how after that first profile of Joe Gould was published, Mitchell had come to believe that Gould’s oral history never existed. Jill Lepore is a staff writer for the New Yorker and a Harvard professor of History. She set out to find out if that oral history did really exist, and the result is her new book, Joe Gould’s Teeth.