The Tourist - Olen Steinhauer

Goodreads 3.78

Milo Weaver used to be a "tourist" for the CIA—an undercover agent with no home, no identity—but he's since retired from the field to become a middle-level manager at the CIA's New York headquarters. He's acquired a wife, a daughter, and a brownstone in Brooklyn, and he's tried to leave his old life of secrets and lies behind. However, when the arrest of a long-sought assassin sets off an investigation into one of Milo's oldest colleagues and exposes new layers of intrigue in his old cases, he has no choice but to go back undercover and find out who's holding the strings once and for all.

In The Tourist, Olen Steinhauer---twice nominated for an Edgar Award---tackles an intricate story of betrayal and manipulation, loyalty and risk in an utterly compelling novel that is both thoroughly modern and yet also reminiscent of the espionage genre's luminaries: Len Deighton, Graham Greene, and John LeCarré