A Perfect Spy by John le CarréRead about another entry on the list.
I'm a sucker for Le Carré. He worked briefly in British intelligence, of course, and it's said that A Perfect Spy is partly autobiographical. Whatever its genesis, it offers mesmerizing insight into what compels a person to follow such a treacherous path.
A Perfect Spy is among Ann Patchett's favorite books, Jonathan Miles's five best books on the secrets of espionage, and Philip Pullman's forty favorite books. Ted Scheinman calls it le Carré's greatest novel.