This is a fairly short and digestible book. It is about Ultra, the handling and uses of itelligence from Enigma traffic, and does not just deal exclusively with the code breaking at Bletchly Park. I found it very interesting, particularly the way that the intelligence picture was built up from fragmentary decyphering of transmissions, logging quantities and geographical sources of traffic and the uses to which it was put. The films often don't make clear that many messages took days or weeks to decode or that decoding failed completely. I shall definitely take a more detailed look at the subject having read this very good book.