Walt Disney: The Triumph Of The Amnerican Imagination by Neal Gabler. Everything you ever wanted to know about Walt you will find in this book.
I bought a book when I was at Disneyland called "Walt Disney: An American Original" by Bob Thomas. I have not finished reading it yet, but it is very informative about Mr. Disney's life, at least what I have read so far.......
There's a really good one by Katherine and Richard Greene called "The Man Behind the Magic" You can find it on Amazon.
I'm working on a book now called "How to be like Walt". It jumps around a bit so if you are looking for something in super cronological order this isn't the book for you, but it is very informative and inspirational and it makes you ohhh so thats why he did that. It has alot of interviews with family and cast that gives you a look at why and how Walt was who is was.
The books by Neil Garber, Bob Thomas & Katherine and Richard Greene are all excellent biographys. If you want to read about Walt's brother Roy I would recommend "Building a Company: Roy O. Disney and the Creation of an Entertainment Empires by Bob Thomas"
I just finished Building a Company. Very interesting. Of course there would have been no Disney as we know it without Walt, but the same can be said for Roy too.