As you can guess, I already own The Imagineering Field Guide to the Magic Kingdom, The Imagineering Field Guide to EPCOT, and The Imagineering Field Guide to Disney's Animal Kingdom at Walt Disney World, so I was quite glad to receive The Imagineering Field Guide to Disneyland yesterday.
That volume has all the flaws and strengths of its predecessors: the stories it contains are way too short for Disney historians but are also a great springboard for new Disney enthusiasts, giving them the basis to move later to more serious books like The Nickel Tour. This being said, when it comes to the newest attractions the series always contains a few stories that we had never heard.
The same can be said about the artwork: since the books are way, way smaller than art books (after all they are pocket books that are meant to be used during a trip to the parks) the artwork's format is way too small and you are better off getting books like The Art of Disneyland or the upcoming Art of Walt Disney World. But the authors seem to know this and offer us in each volume enough never-seen-before renderings to make the books interesting.
In summary: Great books for beginners, a few gems for historians.