I bought this guidebook a few days before I left for WDW with the family. I am glad I did - before that, I had not realised how big WDW is and how useful this book would prove to be. It covers an incredible range of needs (for every type of person, I would say) so you would need to be selective when reading it, especially as it is so detailed. It proved extremely useful though as it helped me negotiate my way around the parks, chose suitable rides for everyone in the family, when to go to the rides, whether and when to queue or go for a FastPass, select suitable restaurants and cafes to eat in and how to reserve tables, how to beat the queues, etc. It also gives a lot of factual information on the attractions which you would not find anywhere else.
Much better than any other standard guidebook - definitely recommended but be prepared to find the time to read it!