I don't see a forum for the Book so I am creating this post for people to perhaps post errors from the book for the second edition?
I've contacted Justin to follow this up ... and thanks for taking the time to notify of this.

2. Page 14 "I rate the Yamaha Pacifica guitars (which start around 200/300)."
this sentence its incomplete it does not specify how these guitars are rated.
This sentence means in his opinion they are worth buying ... to rate something can mean you are going to give it a score .. a mark out of 10 perhaps, as you are thinking ...
But 'to rate' something also means you have a good opinion of it and think it to have many qualities.
Example:
I rate Mark Knopfler 10 out 0f 10 as a guitar player.
I rate Mark Knopfler as a guitar player.
Both are equally valid ways of saying I hold him in high regard, I think him very good.
3. The What guitar should you buy? section is missing the important task of having someone that knows how to play like the guy at the store or a friend play the hell out of the guitar to make sure it does not go out of tune after 3 minutes of playing, my 350 dlls first electric guitar (a shecter) G string came off tune when bending. it was very annoying to have to tune it every few minutes. I also tried a epiphone when I was replacing it and it had the same problem (at the store).
That is a very specific and individual problem that you had and is in no way going to be a general buying experience .. .strings can and do go out of tune through playing / bending ... new strings maybe or a poor quality guitar.
4. Page 16 Tuner section says: "Have mercy on those that will listen to you learning and buy yourself a tuner right away!" sounds funny maybe its missing a "while" between you and learning "... will listen to you while learning...."
It works either way ... no need to amend imo.