If you want to use the Windows version of PGP, this is not the book for you.

Simon Garfinkel's PGP is certainly informative and is written in light, breezy language that makes it easy reading for even the least technical. But, sadly, this book is so out of date as to be entirely useless with regard to actually using PGP today.

O'Reilly's PGP book can be divided into two sections. The first section is really a history of cryptography and how PGP fits in this context. I found this section surprisingly enjoyable as you learn about the long and tortuous struggle between the NSA and people who want to promote freedom and privacy. On a more concrete level though, you do learn quite a bit about different encryption algorithms and key algorithms, such as the RSA and Diffie-Hellman as well as other concepts important to cryptography. Admittedly, the history itself makes for pretty interesting reading.

The second section is about PGP usage, and it is very thorough in its coverage. You will learn just about every possible feature in PGP, and how to apply them to a number of possible situations. I like reading this book over the PGP manuals just for the time and care put into it, if not the amusing examples.

One thing other reviewers have rightly touched on is the age of the book. TIme has passed. The RSA algorithm is now free and open, and PGP clone called GPG is now in wide use. I am definitely excited to see a 2nd edition of this book in hopes that it will cover such things.

However, regardless of the age, this book is an excellent primer into PGP and cryptography culture, and newbies like me will certain enjoy reading it.

The book is also quite simple to read, so much so that I felt guilty for "studying" a book that was so easy that I could blow through a chapter in twenty minutes. One final note of importance is that because the book is old (94), it is UNIX-centric, which is quite refreshing in today's environment of applications written exclusively for Windoze.

The second half explains PGP usage and where you can find it online. Unfortunately, a lot of this seems dated -- however, to be fair, the book is over five years old. You'll probably be better off with another resource such as the included documentation.

The first part of the book though is still timely in that it provides a good overview on how PGP was developed. The sparring between Jim Bidzos of RSA & PGP creator Phil Zimmerman is interesting.

The second part of the book details PGP usage. Since most of it references version 2.x, it is heavily outdated. But the book is nonetheless worthwhile if you are interested in the history of PGP. If not, download the free version of PGP and use the documentation.