Long before Judy Garland sang Over the Rainbow, the denizens of Oz had already captivated the American reading public. The quintessential American fairy tale, L. Frank Baum's The Wonderful Wizard of Oz has had a singular influence on our culture since it first appeared in 1900. Yet, as Michael Riley shows, Baum's achievement went far beyond this one book, or even the 13 others he wrote about that magic kingdom.