Do UFOs exist? Was there a cover up? Discover these questions and more High-interest topics, real stories, engaging design and astonishing photos are the building blocks of the XBooks, a new series of books designed to engage and motivate reluctant and enthusiastic readers alike. With topics based in science, history, and social studies, these action-packed books will help students unlock the power and pleasure of reading... and always ask for more Unearthly remains recovered in Roswell A rancher in New Mexico stumbles on something strange. It's like nothing else on Earth. The U.S. Army says...