Though he is best remembered as the creator of The Wonderful Wizard of Oz and the subsequent series of Oz novels, L. Frank Baum’s prolific imagination led him to pen many other tales, as well. The Master Key, which takes the form of a fairy tale or fable that happens to be set in the early twentieth century, follows teenage protagonist Rob Joslyn, an avid experimenter who accidentally summons a strange (but largely benign) demon while working with electricity.