The Tin Woodman of Oz

In L. Frank Baum's "The Tin Woodsman of Oz", (1918) the Tin Woodsman and the Scarecrow are visited by a young boy named Woot who learns that the Tin Woodsman was once a man who loved a young girl of Oz. Inspired, the three of them set off to find the girl. This novel, the 12th in the Oz series, provides a backstory for Oz and reversed a trend of declining sales in the Oz Books, perhaps as a result of a desire for nostalgia amid the carnage of World War I.