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. He is the cocreator, with Jon Klassen, of the Substack Looking at Picture Books, as well as Shape Island, a stop-motion animated series on Apple TV+, based on their best-selling Shapes series of picture books. Mac Barnett lives in Oakland, California. Jon Klassen is the author-illustrator of I Want My Hat Back, a Theodor Seuss Geisel Honor Book; This Is Not My Hat, winner of the Caldecott Medal and the Kate Greenaway Medal; and We Found a Hat. He is also the illustrator of two Caldecott Honor Books, Sam and Dave Dig a Hole and Extra Yarn, both written by Mac Barnett. Jon Klassen lives in Los Angeles.
Klassen's palette is quiet, his weathered backdrops are elegant, and his comic timing is precisely synched to Barnett's deadpan prose. Triangle fools Square, and the story fools readers, too, as they wait for Square to put Triangle in his place, or for the two to reconcile. Instead, Triangle seems to win this round, even if he does finish the book trapped in his own home. Whereas the humor in Sam and Dave Dig a Hole was subtle and sly, this shape showdown is pure, antic buffoonery.--Publishers Weekly (starred review) Barnett and Klassen, whose previous collaborations--Extra Yarn (2012) and Sam and Dave Dig a Hole (2014)--were Caldecott Honor Books, have created a marvelously clever picture book...The simple sentences and repetition are perfect for a young audience, who will be raptly interested in the devious dynamic between the friends. Judging by this offbeat first volume, Barnett and Klassen's planned trilogy is shaping up to be an excellent one.--Booklist (starred review) Klassen's minimalist visuals make for beautiful, surreal landscapes as the shapes go back and forth; Barnett's even-more-minimalist narrative leaves gaps of many shapes and sizes for readers to ponder. Children will be intrigued by the fairy-tale quality of this narrative and may enjoy debating the motivations of its peculiar characters.--Kirkus Reviews Cheeky Triangle and ingenuous Square's quirky relationship is reminiscent of Arnold Lobel's Frog and Toad, but with a twist. Klassen does remarkable things with a minimal canvas--shapes and eyes are all he's got, after all...This weird and wonderful picture book presents a whole new angle on shapes--and friendships.--Shelf Awareness for Readers Both the occasionally repetitive text and the images make this title a good match for emerging readers. The characters convey an appropriate level of shifty expression through the movement of their eyes, and the ambiguous ending will elicit plenty of opinions from young audiences. An understated ode to mischief that's sure to please fans of Sam and Dave Dig a Hole.--School Library Journal There's a lesson about friendship along with an amusing geometry lesson in this charming picture book from the writer-artist collaborators who created the acclaimed Sam and Dave Dig a Hole and Extra Yarn. --Buffalo News This is funny stuff and, as to be expected from Mac Barnett and Jon Klassen, delightfully off-kilter.--BookPage