The History of Espionage by Ernest Volkman
"The History of Espionage" recounts the fascinating story of spies and spying from the cloak-and-dagger machinations of the Ancient Greeks and Romans to the high-tech surveillance operations of the post 9/11-world. It is a tale of clandestine agents, military scouts, captured documents, dead-letter drops, intercepted mail, decoded telegrams, secret codes and ciphers, bugging devices, desperate plots and honey traps.