As a former librarian, your question really struck a chord with me. There are shops throughout WDW that sell books, including books about Walt Disney himself. While the selection of titles available at WDW is not large, you can reliably find the basics at the Writer's Stop located next to the Sci-Fi Dine-In at Disney's Hollywood Studios and at the Once Upon a Toy store at Downtown Disney. One particular title I've seen in both locations is Neal Gabler's book "Walt Disney: The Triumph of the American Imagination."
While you can find information about Walt the man at WDW, I wouldn't wait until you arrived at the parks to do your reading. The Gabler book, as well as MANY others, is available at regular book retailers and through Amazon.com. Just a quick Amazon search on "Disney biography" gives a range of titles for both children and adults. There are also countless titles about the development of the parks, the influence of Disney on American culture, the making of the Disney films, and so on. I list just some of the books in my personal Disney library
HERE.
If you have a chance to do a bit of reading before your trip, you might find that some of the insights you find in the books will give you a greater understanding of and appreciation for some of the elements of the parks. I love learning about the history and development of the attractions I'm experiencing.
Happy reading and have a wonderful time at Walt Disney World.