We found that book extremely helpful in sorting out "good" trails. It will also save you a lot of time locating trail heads. Ratings are given too. Some of those back country roads are complex meaning it's very easy to get lost. Accurate directions are a must.
This guy got stuck on a rock on his way to Crown King, AZ. Terrain in here is much tougher than it appears.
Trail ratings are important and can help you avoid accidents and snags. Know before you go! Good luck and ride safely.