Leslie Iwerks' new book The Imagineering Story is a masterpiece, which comes as no surprise.
What is astonishing is the fact that this 700+ book is not an art book. This is wonderful and (to me at least until D23 Expo) totally unexpected news. In other words, those 700+ pages are practically pure text. Hurrah!
In addition, Leslie does something that I love: she focuses on the men and women of Imagineering. He book is mostly based on interviews.
This means that, like Leslie's documentary on Disney+, from a historical standpoint, the book becomes stronger and more detailed as it progresses closer to our time period.
I suspect that to understand in detail the full story of Walt Disney Imagineering one will need to read both Leslie Iwerks' massive volume, as well as Tom Morris' upcoming series of 4 monographs about the early days of Imagineering (to be released by the Hyperion Historical Alliance Press).
Between the two of them they are in the process of revolutionizing our understanding of Imagineering history.