The Royal Book of Oz

The Royal Book of Oz (1921) is the fifteenth in the series of Oz books, it was written entirely by Ruth Plumly Thompson. Beginning in the 1980s, some editions have correctly credited Thompson, In which the Scarecrow goes to search for his family tree and discovers that he is the Long Lost Emperor of the Silver Island, and how he was rescued and brought back to Oz by Dorothy and the Cowardly Lio