I don't usually bother with straightforward trivia books (they are often inaccurate), but some excellent reading with lots of behind the scenes info are:
Walt Disney's EPCOT Center (1982), all about the park, including the abandoned projects such as the Germany boat ride, Japan show, Africa pavilion, etc. EXCELLENT book, and usually fairly cheap on half.com or ebay. Be sure to get the 240-page version, and not the abridged Special Edition
Imagineering (1996), a wondeful book filled with concept art and interesting info
Since the World Began: Walt Disney World the First 25 Years (1996), also a great book with neat information
Also of interest are the various biographies of Walt Disney and Michael Eisner (I like "Keys to the Kingdom"), as well as Storming the Magic Kingdom, which describes Disney under Ron Miller and Ray Watson, and how the company was almost destroyed in the 1980s.