The guides themselves were actually fantastic. Ground breaking in their ability to tie rarity to price, the coverage of more than one state, color pictures, compact to carry.
While some of the information is out of date by now, if you haven't seen it, get the last one, it's pretty amazing.

My only issue with it is the use of the word "Official" which implies an endorsement from some organization or entity. I personally think it was intentionally misleading.