If there is one thing that makes the Dismal Science a shade less dismal, it’s money, as in currency. As Adler points out up front, “People want money because it can be used to buy things.” Right, but as a thing in itself, it’s pretty fascinating. Animals as money, rocks, feathers, salt, fishhooks, purple beads made from clamshells are all intriguing—including their drawbacks, like your money dying on you if it happens to be a donkey—as is Adler’s elemental explanation of bartering and exchange and the gradual evolution of money from precious metal to artful paper to the woefully drab plastic and digital varieties. Adler is less successful trying to make sense of how money reflects value, explaining that when the cost of ice cream goes down a dollar may buy an extra scoop but not getting at what circumstances may cause this. Miller’s flat, digital artwork is solid throughout, providing a cheery Uncle Sam as a guide with simple stylized images set to swaths of yeasty color, flowing easily with the narrative and surprisingly emotive. (Informational picture book. 4-8)