 Baum favored book publication for the stories; when his health declined in 1918, he worked to prepare books for future publication in the event of his death.Baum readied three manuscripts, so his publisher (Reilly & Britton) could issue annual Baum books through 1921.Two of those books were the last two in his Oz series ("The Magic of Oz" and "Glinda of Oz"), which were published in 1919 and 1920; the third book was "Animal Fairy Tales".