Rocco, the alias for a New Jersey cop who infiltrated the Mafia in the 2010s, vividly conveys the challenges and perils of undercover work in this gripping if inadequately sourced memoir. Rocco, the son of a policeman, grew up in Bayonne, N.J., playing with kids whose relatives were in the mob. After he barely graduated from high school, his father’s reputation enabled him to land a spot with the police. He quickly began undercover work, and his talent at dealing with people and the unexpected led to him being assigned to work with the FBI. In 2012, he was tapped to make a drug buy off a dealer named Jimmy Smalls, who was supplied by an associate of the DeCavalcante family (supposedly the inspiration for TV’s Sopranos). Rocco’s relationship with Smalls led to his gathering evidence against the DeCavalcantes and the Gambinos, and in 2015 to major arrests. Rocco had numerous close calls with exposure, and the strain on his marriage and family, he writes, was significant . . . Fans of FBI agent Joseph Pistone’s Donnie Brasco: My Undercover Life in the Mafia will want to take a look.