I'd like to partecipate, too.
I read most of "Part 1" and it seems quite understandable and easy to follow for the general public. I'm actually familiar with those concepts, so even I'm trying to be objective you may still consider this comment a little biased.
I noticed that there are a lot of pictures about asymmetric cryptography, while the explaination of symmetric cryptography (3.1) has not a related picture in-page. Something related to bad guys intercepting the key may be an idea.
Just to be picky, in 4.6 there are some (misplaced?) dots.
Keys are the basic component of asymmetric. cryptography, also know as public key cryptography.
To be used they must be stored in key rings., which GnuPG creates automatically.
Hope this helps.
You're in, good luck, enjoy the book! Thanks for the feedback and for pointing the mistakes, that's very helpful. Because the book was not edited with the professional quality you might expect from a professional publisher you may find some occasional mistakes, we are aware of them. It would be difficult for us to update a version every time a new mistake is found, but we are taking notes of them and considering making an errata section. Another reason is because the book will be released in public domain soon.