This book has good information, but it is really hard to use. It has campgrounds listed by city / town and the cities & towns are listed alphabetically by state. As a result, if you are looking for a campground in a particular area, you need to look up every city & town in the area separately. This is an almost impossible task if you don't know every little town in the area you want to camp. I think it would be far easier to navigate if the campgrounds were listed by county. That would at least give you all the campgrounds in a particular area. What's even easier, is to use the free Woodall's website to search. You can search that by city and it will give you all the campgrounds in the area, even if they aren't in the specific town.
The book also has some good coupons, which if you use would probably pay the cost of the book. It will also be handy to have as a reference while on the road without an internet connection.
I would recommend buying it for the coupons alone, but do so with the idea of using their website to do most of your searching for campgrounds.
3/11/12 Update - I realized that I did not explain my "incomplete" statement above. I have found that there are a lot of campgrounds that are not listed in Woodall's. I was using it to try to find a campground near a family reunion and getting very frustrated. Once I stopped using Woodall's (and its website) I found a lot more locations.
I'm also not sure that I still think it is worth buying this for the coupons. Most of them are for RV gear and accessories. If you are just starting out and need to buy a lot of stuff, it might be worth it. Otherwise, you probably will not pay for the cost of the book with the coupons.