I really enjoy Since The World Began. I think it's the best official WDW history book the company has released.
The Imagineering Field Guides are also nice, but suffer a little from the amount of corporate spin they include.
If you like art and design both "Building a Dream" and "Designing Disney's Theme Parks" look at the world from an architectural standpoint. They both have great pictures and illustrations, many of which I've never seen in print before, but the text is overly critical of Disney, so wearers of rose-colored glasses beware!
Jason Surrell's Haunted Mansion and Pirates of the Caribbean books are also great must-have books for fans of those specific attractions.
The Walt Disney Imagineering book is also pretty nice. I have the older hardcover version, but it's available again in softcover and it's a pretty good look at WDW, but again a little heavy on corporate spin.
One of my favorite books is Walt Disney's EPCOT - Creating the New World of Tomorrow. Published in 1982, it shows in detail EPCOT in its most early stages. Be aware that there are two versions of this book, one just over 100 pages and another almost 300 pages. Only the longer one is really worth the time and money to track down, but both appear on eBay pretty frequently.
All of the Disney World souvenir picture book have a strong emphasis on the present, with little information on history. If you're interested in WDW history try to track down the older versions. Walt Disney World: The First Decade is a nice look at pre-EPCOT Walt Disney World. It's still fluff, but at least it's vintage fluff.
And finally, probably my favorite book is Disneyland - The Nickel Tour. It's not about WDW, but there has been NO better book on Disneyland theme park history, hands down. I wish ALL of Disney's books followed the lead this book set, and it's a real shame they have only reprinted it once. THIS is the kind of book that needs to stay in print.
