Although the writing is dry in places (especially at the start), this is a fascinating insight into the NSA and signals intelligence. The book doesn’t go into details about how the NSA breaks codes; recent years have seen plenty of books on codebreaking. Instead it focuses on the history of the NSA, the tough, dangerous, yet often tediously boring job of signals operators in the field, and the role that electronic intelligence gathering has played since the Second World War. But as well as notes of historical interest, Bamford has dug up an astonishing amount of inside information about incidents that security agencies and politicians would prefer stayed buried. His desciptions of incidents surrounding the lead-up to the Cuban missile crisis, and the Korean and Vietnam wars are eye-opening. He digs deeply into the question of who knew what and when, and comes up with some shocking answers. Definitely a must-read.