"An Unplanned Life" is the scintillating memoir of George Elsey, a small-town kid from western Pennsylvania who, at age twenty-four, was assigned to Franklin Roosevelt's top-secret intelligence and communications center in the White House. As an officer in the U.S. Naval Reserve, Elsey helped brief the president and his senior associates on war events. He and his map room colleagues acted as the secretariat for Roosevelt's cabled exchanges with Winston Churchill, Joseph Stalin, and Chiang Kai-shek; filed records of "summit conferences"; and stored in safes plans for future operations. Elsey's duties continued with Harry Truman's succession to the presidency. In 1947, he shed his Naval Reserve uniform and joined the White House's civilian staff as assistant to the special counsel to the president. In 1949, he became administrative assistant to the president, and, in 1952, he became a member of the Mutual Security Agency staff....