PGP & GPG is another excellent book by Michael Lucas. I thoroughly enjoyed his other books due to their content and style. PGP & GPG continues in this fine tradition. If you are trying to learn how to use PGP or GPG, or at least want to ensure you are using them properly, read PGP & GPG.
Content-wise, PGP & GPG covers just about everything I would like to see in a book on encrypting email. Lucas addresses Windows and Unix options, both commercial and open source. I only paid real attention to sections on GPG and the Thunderbird Enigmail extension, since that is what I use.
Style-wise, PGP & GPG is incredibly readable. Email encryption could be a dense topic when covered by another author. Lucas addresses the right points, in the right order, with the right attitude. He's one of my favorite authors in this regard. Certain tips he shares, like setting keys to expire annually, or CC'ing yourself when sending encrypted email, or mentioning smart cards for keys, really make a difference. I agree with previous reviewers who liked the task-oriented chart on p. 14 -- that is awesome.
PGP & GPG is definitely a winner. The word "practical" in the subtitle could easily apply to the message of this book.