Bob Thomas actually interviewed Walt himself several times, and witnessed the construction of Disneyland, so he had a firmer grasp on Walt's personality than Gabler did. Also, it seemed to me that Gabler, at times, wrote his book with a bit of a slant to appeal to the bash-Walt crowd - although at least he didn't overdo it TOO much. In my opinion, anyway. Diane Disney, Walt's daughter, absolutely hated Gabler's book, especially his portrayal of her parents' marriage, and chided the Disney company for helping Gabler write it. Her words on the subject, as written by Michael Barrier, author of the great book "The Animated Man - the Life of Walt Disney":
I've often criticized Neal Gabler's book, Walt Disney: The Triumph of the American Imagination, for its many factual inaccuracies and for its misrepresentation of Walt Disney himself. My dislike for Gabler's biography is shared by a very important member of the Disney family. Early this month, Diane Disney Miller, Walt's surviving daughter, sent a fax to a number of executives at the Walt Disney Company, denouncing the book as "a monstrous piece of libelous junk. My parents were not the people he creates in this book, and I cannot understand why all of you who aided and abetted Gabler in writing this book, and who praise it and promote it, can do so without suffering serious qualms."
http://www.michaelbarrier.com/Essays/Diane_On_Gabler/Diane_On_Gabler.html