This book's subtitle unabashedly proclaims it to be "A Rationalization And Extrapolation Of The Split-Level Continuum", a bit of obfuscation which prepares us for this attempt to bring logical scientific analysis to the astounding world of Frank L. Baum's beloved Oz books. Whether such a thing should actually have been attempted is clearly a matter of taste, but it seems likely that fans of the Baum books who also enjoy science fiction will find this novel an amusing blend of wild fantasy and desperate rationalization. The hero is Hank Stover, a World War I veteran flier and barnstormer (and coincidentally, son of the legendary Dorothy), who flies his Jenny (a Curtiss JN-4H biplane) into a mysterious emerald haze and comes out in the wonderland described by his mother many years before. As might be expected, Farmer has to go to considerable lengths to explain the world of Oz, with its talking animals, sentient objects, warring witches, and diminutive inhabitants. He makes some "corrections" to the original Oz books, changes that he asserts Baum made in order to conform to the mores of the age, or the needs of the narrative, or even simple disbelief at Dorothy's eyewitness account. Even given these points, though, Farmer has to resort to some very shaky scientific assumptions, and there are many points which he simply has to call "magic", i.e., the result of a technology that is far beyond ours. Unfortunately, the biggest weakness of this novel is not the science, but the matter-of-fact way that Farmer relates this science fiction take on a classic fantasy -- with very little wonder and a minimum of enthusiasm. Instead, we get a straight-ahead action/adventure without any trace of humor or irony. By constantly trying to explain the principles behind the marvels, he robs the story of its magic (not literally, but emotionally), and by focusing on conflicts between Oz' various factions, he eliminates most of the fun as well. There's plenty of action and some interesting battle scenes, including one between two witches, and a fateful altercation between Glinda the Good and President Harding, but most of this book is pretty standard modern-meets-medieval stuff. Lacking the joy and innocent wonder of Baum's stories, this book seems destined to please readers who loved the Oz books as children, but outgrew them and turned to science fiction instead. They'd do better to re-read Baum's classics, since Farmer's Oz is not really such a wonderful place.