If you are in a bookshop browsing you can always have a look at a book to see whether it meets your needs. However, if you want to find something to meet a need you may well be looking at reviews to decide whether it is worth the effort to chase your local supplier to get a copy. Naturally, suppliers are not happy to get books that they do not sell. My reason for highlighting the obvious is that book titles sometimes fail to provide an adequate description. What do you expect from this book? Well its sub-title might help a little: ' Julius Caesar, the Enigma, and the internet.
'This is a curious book because it is a mixture of history and technical information. In my opinion this has led to it falling between two stools. The casual reader who wants to find out something about the history and how we got to where we are now will find too much technical content and be put off by the exercises (there are solutions to most of them given at the end of the book). The technical reader who wants an in depth treatise on the technology past and present will, I think, feel that the book does not go far enough. The casual reader will be daunted by some of the mathematics while the mathematical reader will be left irritated by wanting to know more. At least this second group will have the advantage of a substantial number of references given at the end.
So what is this book and who is its intended audience? Not the casual reader, nor the specialist student. I think this book is intended for a supplementary course for those studying aspects of information and communication technology. They must have a reasonable mathematical grounding but not an expectation that they will learn the details of current encryption techniques.
Here is a quote from the author's Preface:
It is the author's belief, based on experience, that there is a middle way and that, without going into details, it is possible to convey to non-specialists the essentials of some of the mathematics involved even in the modern cipher systems...
I think that exactly describes this reviewer's problem with this book. I doubt that it would hold the attention of very many readers. The requirements are more restrictive than the author believes. The reader needs a degree of mathematical competence (and confidence) without wanting to know that much about the fine detail.
I suspect that the right place for this book is in a library to serve as a kick of point for study. The book in itself will not satisfy but it might help get an interested student started.