John le Carre's novels often focus on the subject of SPYING. His works explore the moral ambiguity of espionage and the complex relationships between spies, governments, and their enemies. Le Carre's most famous novel, Tinker Tailor Soldier Spy, is a classic example of his exploration of the world of espionage. The novel follows the story of a retired British intelligence officer who is tasked with uncovering a mole in the British Secret Service. Le Carre's other works, such as The Spy Who Came in from the Cold and The Constant Gardener, also explore the themes of espionage and its consequences.