Andy and Terry's amazing treehouse has thirteen new levels (it used to be 13 storeys, then 26, but they keep expanding!) They've added a chocolate waterfall you can swim in, a volcano for toasting marshmallows, a bulldozer-battling level, a baby-dinosaur-petting zoo, a not-very-merry merry-go-round, a boxing elephant called the Trunkinator, an X-ray room, a disco with light-up dance floor, the world's scariest roller coaster and a top-secret thirty-ninth level which hasn't even been finished yet! And this year 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!