The 13-Storey Treehouse is the first book in the hugely successful, absurdly imaginative illustrated children's series. The book's protagonists are Andy and Terry, who live and work in a massive treehouse they have built, which features thirteen amazing (and ridiculous) levels, including a bowling alley, a tank of man-eating sharks, and a lemonade fountain. The plot centers on the chaotic process of trying to write a book for their grumpy publisher, all while dealing with the endless distractions and silly adventures their bizarre treehouse provides.