The book is comprehensive. At times boring, at times fascinating, it gives an in depth look at codes and code breaking through history. The book was published in the 1960s so the WWII coverage is lacking especially in regards to Ultra (this may have been corrected in a later edition) and the latest chapters chronologically, especially the one on the NSA should be 10 pages long, not the 30-40 that they are. In addition the author has a very triumphal tone with an Anglo-centric stance periodically that is particularly grating. Outside these issues the book is quite good at laying out both the nitty gritty of the codes themselves, the people that invented and cracked them, and their impact through history. The last few chapters are not specifically about code breaking, covering among other things translations of lost languages and code breaking in literature. They are however interesting in and of themselves. Worth reading unless and until someone comes out with a new, better written historical survey.