It has arrived! We found an affordable copy on Alibris, after losing an EBay auction for another reasonably priced one (got it for cheaper than EBay too!) - and my son has been devouring it.
He is practicing geography, 2D art, language, story chronology, narration, plot development, answering what-if questions, creating costumes, re-enacting with Legos, blocks, counting bears, and SO MUCH MORE.
I have to say, I am still not convinced that the Land of Oz stories are on par with Narnia or other such stories, but they are perfect for a little boy who is reading 5-6 grade levels above his age yet still needs something developmentally appropriate, funny, enertaining and that connects to so many other subjects.
Now if I could just read it for myself!