By now the story of the cracking of the german Enigma code seems to be well known, with books and movies all over the place. But a lot of that (especially in fiction) is overly generalised and lacking in background ... to nobody's surprise. This book is the real deal. It has all the background info and the back story. I guess it's not a spoiler to say that the story starts way, way before Alan Turing does his things.

The book starts with the almost first contact of french and polish cryptographers with the enigma mistery encryption. It then covers the arc of the war, mostly but not exclusively centered on the battle of the atlantic. It stops after the allied invasion of normandy. I think it's right to give a lot of attention to the battle of the atlantic, because the real story is on how the code had to be cracked open again and again around that battle, and because the pinching of code books mostly happened there. But the other pillar of the book is how the secret of having broken Enigma has to be protected, and was almost revealed so many times over.

The book is also expectedly british centered. The polish, french, and american codebreakers and admins all take part and are given credit, but this is the british point of view.

This books makes a good union between giving the background information and/or technical details (there are huge appendices with lots of detailled explanations) and the lively stories that give you the human blood in all this. Which makes for good reading.