In November 1960, Frank Sinatra gave Marilyn Monroe a dog. His name was Mafia Honey, or Maf for short. He had an instinct for celebrity. For politics. For psychoanalysis. For literature. For interior decoration. For Liver Treat with a side order of National Biscuits. Maf was with Marilyn for the last two years of her life, first in New York, where she mixed with everyone who was anyone—the art dealer Leo Castelli, Lee Strasberg and the Actors Studio crowd, Upper West Side émigrés—then back to Los Angeles. She took him to meet President Kennedy and to Hollywood restaurants, department stores, and interviews. To Mexico, for her divorce. With style, brilliance, and panache, Andrew O’Hagan has drawn a one-of-a-kind portrait of the woman behind the icon, and the dog behind the woman.