David Kahn's Seizing the Enigma is a detailed effort to tell the story of how the German naval code was broken. Though that intelligence breakthrough of WWII is widely known, little is known of how complicated the effort was. It required the effort of brilliant mathematicians working the theoretical side and the bravado of British naval and intelligence officers who literally risked their lives to obtain the information and equipment needed to crack the code. Kahn gives a very detailed story and it is at times a bit thick and difficult to follow. This is only because the theory behind the enigma was so complex and a complete history of the saga requires at least some examination of the intriguing, yet, sometimes confusing mathematical concepts. In all, a good read.