After Triangle plays a trick on Square, Square plans to reciprocate but runs into trouble when he tries to enter the triangular doorway of Triangle's home.

Meet Triangle. He is going to play a sneaky trick on his friend, Square. Or so Triangle thinks… With this first tale in a new trilogy, partners in crime Mac Barnett and Jon Klassen will have readers wondering just who they can trust in a richly imagined world of shapes. Visually stunning and full of wry humor, here is a perfectly paced treat that could come only from the minds of two of today's most irreverent -- and talented -- picture book creators.

Mac Barnett, the 2025-2026 National Ambassador for Young People's Literature, is a New York Times best-selling author of stories for children. His work has been translated into more than thirty languages and sold more than five million copies worldwide. Mac Barnett's books have won many prizes, including two Caldecott Honors, three New York Times/ New York Public Library Best Illustrated Children's Book Awards, three E. B. White Read-Aloud Awards, the Boston Globe-Horn Book Award, Germany's Jugendliteraturpreis, China's Chen Bochui International Children's Literature Award, the Netherlands' Zilveren Griffel, and Italy's Premio Orbil. Mac Barnett lives in Oakland, California. 

Part of the Shapes Trilogy, the books that inspired Shape Island from Apple TV