This is an excellent book that focuses on the use of the intelligence they derived from breaking the German encoded signals (mostly from the famous Enigma machine) not how they broke it. Its a very interesting insight to how they distributed this information with the Special Liaison Units and the extreme care they took with their reactions to ensure the Germans didn't guess they were reading their signals. They always tried to provide an alternative means for obtaining the information.
Winterbotham is in an interesting position as he handle the overall operation of distributing this information to the field, strategic decision makers and he regularly briefed Churchill on the information gleaned. It covers some very important events but also has small interesting detail as well such as the fact he often had to stay up late on a Saturday night to brief Churchill after he'd watched his regular Saturday night film.
The book is broken down into the major campaigns of the war across 22 chapters and 190 pages of small print; no pictures. Covering battles in Europe, Africa and Asia. The one area not touched on too much is the Atlantic which was handled separatly by the Navy itself.
The writing style is easy to read and engaging. This doesn't claim to be a history of the war but cover how intelligence (Ultra) is use in the field and strategically, and the level to which it was used. However given how many areas it is used in it does feel pretty comprehensive and put some of the battles in perspective.
I read the 1974 published edition and it does gives a brief account of how the code is broken but from the other books I've read this is not correct. Try The Hut 6 Story for details of what went inside Bletchley Park. But this book does make a great complement to Hut 6 showing the other end of the stick. Its Fascinating to see how much information was being read and distributed and that the Germans never knew. What is also interesting is how people used the information. Patten made maximum use of it, Montgomery less so who seems more to bear it in mind but acts more 'fairly' as if he didn't know in planning his approach. This direct comparison is specifically made in the book.