Having expanded their treehouse to an astonishing thirty-nine stories, Andy and Terry describe the invention of their "Once-Upon-a-Time machine," which they have designed to write and illustrate their stories for them Andy and Terry are once again inviting readers to come hang out with them in their astonishing 39-story treehouse (it used to be 13 stories, then 26 stories, but they keep expanding). And this year they will have even more time to jump on the world's highest trampoline, toast marshmallows in an active volcano, swim in the chocolate waterfall, pet baby dinosaurs, and go head-to-trunk with the Trunkinator, since Terry has created the greatest invention that he-or anyone else-has ever invented . . . a Once-upon-a-time machine that will write and illustrate their entire book for them! Join New York Times-bestselling author Andy Griffiths and illustrator Terry Denton on another wild storytelling adventure in a series Publishers Weekly described as "Anarchic absurdity at its best." Welcome to The 39-Story Treehouse...What are you waiting for? Come on up!This title has Common Core connections.