Lovable, circular Charlie Piechart is back with a new mystery, this time one designed to teach us about shapes. Along with his sidekick dog, Watson, Charlie is tasked with finding his friend Margot's hat, a necessary prop for the school play (and a perfect cone). In this quest not only do we learn about shapes but also the importance of clues. Comstock depicts familiar school things ckers, an art room, a science lab, a teachers' lounge th pencil, paper, and digital renderings. The simplistic look of the characters and the monochromatic colors place the emphasis on the shape theme, while sidebars add definitions and examples. Shapes are both front and center and tucked away in bulletin boards and costumes. The final pages review the shapes shown, offer a challenge to readers, and give directions for making a princess hat and a rocket (powered by hand). Never fear cautionary note suggests adult help for the more complex activities!

K-Gr 2 The second mystery featuring the boy detective with a pie-chart body is built around shape concepts. When Margot's hat disappears, she asks Charlie and his dog assistant Watson to discover its whereabouts. Their school-wide search for a cone-shaped hat sets up opportunities to introduce and compare cylinders, spheres, and other shapes. Most of the geometry information is woven fairly seamlessly into the mystery plot. A ring of purple sparkly paint, for example, is a key clue but also demonstrates that the bottom of a cone is a circle. The backgrounds of several scenes are peppered with a variety of shapes that catch the eye and support the theme; a few of them are even clues. The mystery is not especially compelling, and the geometry content is strictly introductory, but the combination works pretty well. Retro-style illustrations lend a slightly goofy tone, adding just the right touch of humor to the otherwise straightforward narrative. Observant readers will notice visual hints about where the hat might be; even the dog figures it out before Charlie. A final scene reveals that the principal's hat has also been missing, prompting readers to trace backward to find out how it wound up on Watson's head. Two simple projects at the end have instructions for creating a hat and a rocket; both items tie in neatly to the story and to the featured shape of the cone. VERDICT A good choice for libraries in need of more STEM-related materials. Steven Engelfried, Wilsonville Public Library, OR