Haven't read the book but agree this is great adviceThe biggest single mistake made in getting any dog, but which can be critical with large, potentially dangerous (but actually wonderful) breeds like the GSD, is selecting based upon looks and not temper/dominance. Also, I will second the note above that if your son isn't committed to regular daily exercise and interaction - don't get a GSD, it will end in frustration for all. These are pack oriented working dogs not lap dogs (in general) not to be left alone all day or kenneled - IMHO - without very bad results.
My 2 cents.
BTW - I love this breed and with good selection, considering how your son can and will live, they can make the most loyal and faithful of pets/companions (I will not say "fur baby") because the human is not a parent he/she is the owner and master...if not then the dog will be.