A variety of shapes in different colors, forms (solid, outline only), and configurations (three-sided, four-sided, open and closed, etc.) offer ample opportunities for engagement as readers are repeatedly invited to answer the question “Which one doesn’t belong?” The opening example shows four shapes and is followed by four page spreads articulating the reason for four possible answers. “All of these answers are correct! … The important thing is to have a reason why.” Ten subsequent spreads show differing series of four shapes and invite children to come up with and explain their own answers for why one doesn’t belong. “You’re thinking in a mathy way when you notice sameness and difference for one property [e.g., straight sides, number of sides, solid, etc.] at a time.” The author adds, “the properties are more important than the words you use … if you use words such as smooshed, stretched, bent, dented, curvy, colored in or cupcake while reading this book, you’re probably doing some great math!” (Ages 5–9)