Fifty Dead Men Walking by Martin McGartland

A firsthand memoir of a young Belfast man who secretly infiltrates the Provisional IRA and becomes an informant for British security services, detailing the dangerous double life he leads as he feeds intelligence that helps thwart numerous bombings and assassinations, the moral compromises and fears that come with betrayal, the growing sense of isolation as his handlers and comrades fail to protect him, and the eventual exposure and flight that leave him grappling with the long personal cost of working undercover.