As bibliography in the back of this book indicates, it's an exhaustively researched piece of work, seemingly leaving no stone unturned in the authors quest to tell the whole story of the cracking of the enigma code from its inception in the early 30's right through to the end of WW2. It may be that this exhaustiveness is what leads to the books' greatest weakness - the leaden, lumpen prose in which it is presented.
The breaking of Enigma was a major acheievement by British intelligence and undountedly lead to the war being shortened, possibly by years; it is a tale of individual courage and of genius, and of the constant race against time to break the messages of the day in the hope of protecting british shipping in the Atlantic.
Sadly, none of this excitment or even interest is conveyed in the writing, and whenever a player in this grand tale seems about to develop a life of their own the authorial hand moves quickly to push them back into the grey, uninvolving prose.
This is a shame; it's a great story, worthy of being often told - but this book - whilst crammed with facts - does not tell a story, more lists dates and names and forces the reader to try and find their invlovement or interest where they may.
Five stars for research and information, one star for writing. A tremendous shame.