David Kahn's newest book updates his previous work, which sits on every Cryptographer's, Cryptanalyst's, and government Special Intelligence officer's bookshelf in the entire world. If you REALLY want to how ciphers, codes, and systems are broken, Kahn is the author who tells you. Any person knowledgable in the field of Cryptology or Intelligence will tell you that Kahn' book has never been equalled. It is known as "The Bible of Cryptology" within the field.
From early Sparta and Rome to the present day, the strengths and weaknesses of systems and devices are presented in clear, concise terms -- occassionally with a bit of levity, where appropriate. Novices in the field will find much useful -- and highly interesting -- information. Professionals always find reminders of the fallability of "unbreakable" systems.
Kahn's writing style is clear, concise, and analytical. It is never boring.
I was employed by a maker of Cryptographic equipment, and was authorized to discuss key generator and cipher system issues with the heads of national governments. A copy of "Codebreakers" was our most requested -- and welcomed gift. That speaks more eloquently than any words I might craft.