(A K Peters) Intended for elementary age children, You Can Count on Monsters first explains the basic ideas of multiplication, prime and composite numbers, and factoring. Then for each number, from 1 through 100, the book on the left-hand page depicts the number broken down into its prime factors using dots and factor trees; on the facing page is a playful monster that relates to the number. Designed to help children understand the building blocks of numbers, each individual monster represents a different prime number. For example, the monster for the prime number 2 has two big eyes. For each composite number, the scene depicted involves the monsters for its prime factors: the number 14, for example, involves a scene with the monsters for prime numbers 2 and 7. Part of the fun of the book is figuring out how each monster is related to its prime numbers. Schwartz is a mathematics professor at Brown University and a 2003 Guggenheim Fellow.