From the First Step Nonfiction series, this small book introduces a single state of matter: a gas. Each page in the main section offers one or more colorful photographs and a brief line or two of large-print text. After a brief introduction to matter, the discussion moves on to the characteristics of gases and a few examples. The final pages, written in more difficult sentences, include a glossary, an introduction to the oxygen cycle, and a section of "Fun Facts." The explanation is good as far as it goes, but it's puzzling that the introduction to states of matter does not mention solids and liquids. The sentence "There are three kinds of matter" is illustrated with photos of an ice cube in child's hand, water falling into a bathtub, and steam rising from a cup, but the solid and liquid states are not identified in the text. Still, parents and teachers may find the book useful in helping their children grasp the idea of a gas.