This book is useful for ages 4+. "San Diego Zoo Animal Library" gives youngsters the opportunity to learn about many animals, most of which can only be seen in zoos. Some of these animals are endangered. Others are rapidly disappearing from the earth. "The Library" offers the chance to learn about these animals before they are gone forever. And each volume of the "Library" is numbered. Collect them all and provide your child with an encyclopaedia of animal life.