I read pretty much every Disneyland history and fact book I find. Chris Strodder's The Disneyland Encyclopedia: The Unofficial, Unauthorized, and Unprecedented History of Every Land, Attraction, Restaurant, Shop, and Major Event in the Original Magic Kingdom lives up to its massive title.
A simple alphabetical listing of just about every First through Fifth order-of-interest item in the park. Everything from the amazing history of the Golden Horseshoe Review to fun facts about a tobacco shop that disappeared 27 years ago lies between the covers of this book. These are truly encyclopedia style entries and are chock full of facts with less emphasis on story telling. I think it'd be a great book to have at the park.
I did a cover-to-cover read through of this at home. I'd prefer to have it electronically on my phone via Kindle to look at while in the park. Go e-version if you can.