"The very thing!" exclaimed Professor Wogglebug, bounding into the air and upsetting his gold inkwell. "The very next idea!" Devotees of L. Frank Baum's classic children's books would quickly recognize the above excerpt as the opening of the 15th book in the Oz series, The Royal Book of Oz. They might be harder pressed to say whether these lines were actually written by Baum. The book appeared with Baum's name on the cover in 1921, which was 2 years after Baum's death, and it was billed as the final work of the Royal Historian of Oz. For decades, however, fans...