After reading many WDW travel books, the Unofficial Guide is by far the most comprehensive planning guide available. It is a must read for anyone considering a WDW vacation. I have checked out the 2004 edition at my local public library, and will bring it with on our trip.
This indispensible book provides relevant, timely and accurate information, as well as practical suggestions and knowledgeable advice from both a reviewer's and visitor's perspective.
I found the Unofficial Guide most helpful because of its thorough park rating system, meticulous hotel and dining profiles, helpful visitor comments and efficient touring plans.
By comparison, Frommer's outdated guidebook comes across as being overly objective and rather obscure. Even the most recent edition inexplicably continues to offer useless recommendations concerning attractions and events that even the most unseasoned traveler knows have closed long ago (i.e. River Country, Alien Encounter, Discovery Island Wildlife Sanctuary).