A solidly middle-class Frenchman who has the grave misfortune of being a distant relative of Charlemagne is "elected King" of France. Hilarity ensues.
Quite funny. The names of the parliament members (Le Comte de Quatre Chats) and the frustrations of King Pippin's wife that he is not "helping" around the house are quite funny. The idea that France is not France without some sort of revolution (and thus the need for a king) is quite good. Unusual book for Steinbeck, but silly nonetheless.