I used to be a huge guidebook junkie, back when I didn't go as frequently as I do now. I started out with my "official" Birnbaum's guide for 1987 and it became fun thereafter.
I started reading the Unofficial Guide for 1992 and beyond. Passporter started around 1999 or so. What I liked about Passporter was that it became an organizer and guidebook combo, and it was the first guide I've ever seen that had resort maps.
The most useless guidebooks I've seen were the "Idiots" or "Dummies" guides. I had gotten one years ago that was so out of date, it was giving tips on things that were a couple of years out of date. That was poor editing, and I would never recommend those guides.
I would recommend the Unofffcial Guide and Passporter wholeheartedly because they are constantly researching and updating their info.