Someone who already has a bookshelf with every book on Disney park history ever published and who reads every Disney fan website religiously is unlikely to find very much that's new in The Disney Mountains: Imagineering at Its Peak by Jason Surrell. Even then, I would think such a person would enjoy seeing so much brought together in one volume.
But mainstream audiences—ranging from the occasional Disney park guest who just want to learn more to the frequent Disney park guest who visits MiceChat, MiceAge, and Yesterland regularly—should find a lot that's new and interesting in Surrell's book.
I agree that the book is wonderful. But I'm still somewhat puzzled why the "book presents what is presented."
I find it surprising that Tokyo and Hong Kong get so little attention. (In fact, the book doesn't even mention that there are versions of Space Mountain in Tokyo and Hong Kong.) And I'm surprised the so much of the book is about Expedition Everest.
I don't understand the omissions in the first case and the disproportionate coverage in the other case, even if the book is aimed at a mainstream audience.