Roald Dahl penned his first letter to his mother, Sofie Magdalene, when he was just nine years old. The origins of a brilliantly funny, subversive, creative mind were evident in boarding school, and as he entered adulthood, his penchant for storytelling emerged in his missives home from Africa, where he was stationed by Shell Oil, and then from the desert camps of the Royal Air Force. His skills were sharpened after a plane crash in Egypt landed him...