You Can Count on Monsters: The First 100 Numbers and Their Characters [ペーパーバック]

CRC Press Author and NPR's Math Guy Keith Devlin spoke with Scott Simon about how the book makes finding prime numbers fun.

"This is one of the most amazing math books for kids I have ever seen…," Devlin says. "Great colors, it's wonderful, and yet because [Schwartz] knows the mathematics, he very skillfully and subtly embeds mathematical ideas into the drawings."

Another enjoyable math book for younger kids is You Can Count on Monsters by Richard Evan Schwartz. Counting plus monsters = awesomeness.
Andrea Pyros, "Stop the Summer Slide: How to keep your kids from falling behind after school lets out," The RetailMeNot Insider, May 2012

Math is no monster in the clever hands of Richard Evan Schwartz, a math professor at Brown University. With logic and oodles of humor, he makes primes and composites perfectly clear.
The Sacramento Bee, March 28, 2011

This is one of the most amazing math books for kids I have ever seen … Great colors, it’s wonderful, and yet because [Schwartz] knows the mathematics, he very skillfully and subtly embeds mathematical ideas into the drawings.
Keith Devlin, NPR and Stanford University

This delightful book is a result of the author's desire to teach his daughters about primes and factorization. ... The whole thing is a lot of fun. The book is well produced and nice to look at.
Fernando Q. Gouvea, MAA Reviews, March 2010

This compact, innovative book counts to 100 using prime numbers represented as 'monsters,' each with identifying characteristics (two resembles a bee with two buggy eyes, and three is an angry-looking triangular creature). The book opens with explanations of multiplication, prime and composite numbers, and factor trees, then moves on to a list of numbers. Each prime number looks unique, while composite numbers are represented by scenes involving their prime monsters (eight is illustrated as three of the beelike twos, i.e., two times two times two. Readers may have difficulty deciphering the pictures, which come to resemble little works of abstract geometric art. But especially for creative learners, visualizing the roles each monster plays may lead to deeper number sense. Ages 4-8. 
Publishers Weekly, March 2010

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 one through 100, the book’s left-hand pages depict the number broken down into its prime factors using dots and factor trees, and on the facing page, there is a playful monster that relates to the number. The monsters are designed to help children understand the building blocks of numbers. Each prime number is represented by a different monster. ... For each composite number, the scene depicted involves the monsters for its prime factors. ... Young readers can have fun figuring out how the monster is related to its prime numbers. 
Katherine Federici Greenwood, Princeton Alumni Weekly Blog, March 2010

You Can Count on Monsters: The First 100 Numbers and Their Characters by Richard Schwartz has won Best of Category for juvenile books at Bookbuilder's 53rd Annual New England Book Show. This show recognizes the year's most outstanding work by New England publishers, printers, and graphic designers. Judges praised the book's freshness, beautiful illustrations, and unique way of looking at numbers, and called it 'a book for kids and parents.' 
Bookbuilders of Boston, May 2010

Prime numbers are like Antigone, Oedipus, or the Olympic Games: they already interested Euclid, Sophocles and Pindar, and they are always at the heart of the news ... Thus, after a near infinite number of books devoted [to them], a mathematician from the East Coast of the United States has recently published [something] new [about primes] ... [for] ... children ... most pages are strictly without text, with some figures and some very nice drawings. 
Pierre De La Harpe, Images des mathmatiques, June 2010

In this book, the old saying 'A picture is worth a thousand words' has been twisted around. ... There is very little reading in the book; the ideas will become clear from the pictures and drawings. Except perhaps for the very last part, the volume should be accessible for elementary school students, and even for some of them, the last part should not be too difficult. ... Because of the color and the emphasis on pictures, the book may even have some appeal to more advanced students and to adults who are 'afraid' of mathematics, because it doesn’t repeat what they may have already experienced, but instead brings out new ideas with little demand on prior knowledge. 
Donald E. Myers, AAAS Science Books & Films, August 2010