Book set includes three 8.5" x 11" 80 page, case-bound books. The SD-X Reader allows the user to touch pictures and words on the page to learn more information, hear vocabulary words defined, and interact with activities that reinforce knowledge. Each book has about three hours of audio. Set includes: Animals is one of six books in the Encyclopedia Britannica Science Library. It provides an overview of animal life, from invertebrates to amphibians to mammals. Touch the page to hear authentic animal sounds, along with in-depth information and learning quizzes and games. Dinosaurs, Reptiles, and Birds is one of six books in the Encyclopedia Britannica Science Library. It provides information on dinosaurs, snakes, lizards, turtles, and birds in picture encyclopedia format. Under the Sea is one of six books in the Encyclopedia Britannica Science Library. Pages reflect the diversity of life in water, from plants to invertebrates to fish to mammals. Large, colorful pictures introduce the reader to representative species of aquatic life.