Heart of Darkness (1903) is a first-person within a first-person account about a man named Marlow who travels up the Congo River in search of an enigmatic Belgian trader named Kurtz.
The Spy Who Came in from the Cold (1963) by John le Carré is set in the world of Cold War espionage and helped to usher in an era of more realistic thriller fiction, based around professional spies and the battle of wits between rival spymasters.