Book excerpt: Multi-award-winning, New York Times best-selling duo Mac Barnett and Jon Klassen deliver the final wry and resonant tale about Triangle, Square, and Circle. This book is about Circle. This book is also about Circle’s friends, Triangle and Square. Also it is about a rule that Circle makes, and how she has to rescue Triangle when he breaks that rule. With their usual pitch-perfect pacing and subtle, sharp wit, Mac Barnett and Jon Klassen come full circle in the third and final chapter of their clever shapes trilogy.