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.
Merry Go Round in Oz 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 Newberry 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.
Robin Brown from the USA rides a magic merry-go-round horse to Oz. The horse whisks away from Earth and lands in the Quadling Country of Oz. Upon landing, Robin must help find the missing magic circlets of Halidom.