I thoroughly recommend reading this article on PGP, the introduction to PGP & GPG: Email for the Practical Paranoid, then download whatever flavour of PGP you prefer and start using it.
This lawsuit turned Zimmermann into something of a hero in the computer community. Many people downloaded PGP just to see what all the fuss was about, and quite a few of them wound up using it. Zimmermann’s legal defense fund spread news of the PGP lawsuit even further. In congressional hearings about encryption, Zimmermann read letters he had received from people in oppressive regimes and war-torn areas whose lives had been saved by PGP, contributing greatly to the public awareness of how valuable his work had been. Also, PGP was available on the internet before the book was published — the code was available from anywhere in the world. (Admittedly, you needed internet access to get a copy, which was slightly difficult in the early 1990s.) The book was simply a legal device to make it possible for people outside the United States to use PGP without breaking US law.