I was not really sure what to expect from this book. I was interested how cryptography could be described in such a way as it would be suitable for 'dummies', and wondered what the content could possibly be.
It turned out to be a bit of a mixed bag, some of which was potentially useful, while some seemed to be padding rather than sensible content.
On the plus side, the book gave a reasonable summary of the installation of PGP (most examples in the book revolved around how cryptography applied to PGP). In addition, the book gave some good advice on selection and remembering passphrases (although if you read the book from cover to cover you notice a certain amount of repetition in this area).
The book includes some basics - for example, a description of how binary numbers work. Perhaps this is sensible for a book aimed at complete beginners. However, this technical detail was not carried forward beyond a description of the XOR function. (The use of the XOR function in conjunction with a 1-time pad was not explicitly covered). This left me wondering what the intended audience of the book would have made of it.
Other annoyances included little clear overview of how the protocol of use of public keys is used. (A diagram of the interactions required to generate and use a PKI might have been useful.)
In short, this book might be suitable for someone needing basic information about cryptography and cryptographic products that did not want to understand the details. However, in this case I think that there might be several chapters which would not be particularly useful or relevant - the book would condense down to a 'how to use PGP, with some handy hints on remembering your password'.