Frank L. Baum 
Rinkitink in Oz [EPUB ebook] 
Wherein Is Recorded the Perilous Quest of Priical Isles That Lie Beyond the Borderland of Oz

Introducing this Story
Here is a story with a boy hero, and a boy of whom you have never before heard. There are girls in the story, too, including our old friend Dorothy, and some of the characters wander a good way from the Land of Oz before they all assemble in the Emerald City to take part in Ozma's banquet. Indeed, I think you will find this story quite different from the other histories of Oz, but I hope you will not like it the less on that account.
If I am permitted to write another Oz book it will tell of some thrilling adventures encountered by Dorothy, Betsy Bobbin, Trot and the Patchwork Girl right in the Land of Oz, and how they discovered some amazing creatures that never could have existed outside a fairy-land. I have an idea that about the time you are reading this story of Rinkitink I shall be writing that story of Adventures in Oz.
Don't fail to write me often and give me your advice and suggestions, which I always appreciate. I get a good many letters from my readers, but every one is a joy to me and I answer them as soon as I can find time to do so.