Marvelosissimo the Mathematical Magician returns, this time tackling measurement, in this latest installment of the winning “millions” series (If You Made a Million, 1989, etc.). In his systematic and logical style, Schwartz presents an enormous amount of information in an impressively clear and concise manner, beginning with the history of standardized measuring units. Through a series of “bright ideas,” the narrative arrives in the modern day, delving into current methods of measuring weight, length, and volume in the US. However, as the complexities of these systems are revealed, it seems another bright idea is needed, and—voilà—the metric system is introduced. Kellogg’s busy illustrations are jam-packed with color and exquisite detail. With plenty of dialogue (via text bubbles) and tons of eccentric characters from cavemen to kings to unicorns, the art is as fun to explore as it is functional. To give a sense of real-life scale, inchworms are placed next to foot-long snakes, and a hippo’s water bowl is pitted against a cat’s. Accurately sized rulers are depicted, including a foldout meter at the center. A lengthy author’s note supplies further, detailed information about the metric system and a plea to “think metric” in everyday life. Although Schwartz’s intention is to make a point about the relative simplicity of the metric system, he does not neglect American standards, and thereby keeps the work relevant—it can serve as an introduction to measuring, and can also function as a reference guide. The Schwartz-Kellogg team has got it right again: this should be part of every professional’s collection. (Picture book. 5-12)