Gr 3–5—These introductions are of uneven quality. Planets sometimes uses incorrect grammar and problematic definitions, e.g., Earth’s gravity is said to be “strong enough to move other objects out of its path.” Uranus is described as being tipped on its side perhaps because it crashed into something big. Moon provides excellent simple explanations and explains why our Moon’s near side always faces the Earth. Sun uses attention-getting comparisons; e.g., the temperature of its outer layer is cited as 50 times hotter than boiling water, and almost one million Earth-size planets could fit inside it. Stars contains straightforward definitions, e.g., “a sphere is a shape like a ball.” Each book has at least one simple activity, and ethnically diverse boys and girls are shown either on the cover or in illustrations. Each chapter spread has several full-color photos and a few paragraphs of text.