Merry Go Round in Oz (1963) is the fortieth of the Oz books created by L. Frank Baum and the only one written by Eloise Jarvis McGraw and Lauren McGraw Wagner (her married name was dropped from reprinted editions after the marriage ended). It was illustrated by Dick Martin. It is the last of the "Famous Forty" and the last "official" Oz book. Reilly & Lee had refused many other authors, including previous author Rachel R. Cosgrove to publish a fortieth Oz book because of poor sales, but were persuaded by McGraw's two Newbery Awards to admit a fortieth book into the series. It was published only in the so-called "white edition" and is the rarest book in the series in its original printings. Halidom and Troth are two adjacent principalities within the Land of Oz, both resembling medieval kingdoms. Heir to the throne of Halidom is Prince Gules. The people of Halidom have always derived their physical and mental abilities from three golden circlets worn by their ruler: the first on his right thumb, the second on his right forearm, the third around his forehead. The first and third circlets have been lost, with attendant loss of abilities by the subjects of Halidom. Fess is a young pageboy in the household of Prince Gules, but Fess was born in Troth, so the circlets have no effect on him. Awakening one day to discover that all the natives of Halidom are strangely languid, Fess learns that the second (and last remaining) circlet has been stolen. He embarks on a quest with Prince Gules, aided by a unicorn and a Flittermouse (a talking bat) to retrieve all three. (via Wikipedia)