Cambridge Discovery Education Interactive Readers are the next generation of graded readers - captivating topics, high-impact video, and interactive exercises designed to motivate and engage. Dinosaurs, Richard III, King Tut, the first humans to walk the earth...discover what we can learn about the past by studying bones. Use your unique code insdie the book to access the online reader, complete with videos and interactive exercises. Word count: 2353. Lexile reading level: 520L.