Theme: Area 51, aliens, military, spy planes, mysteries. There is a top secret U.S. Air Force base in the Nevada desert. The government won't talk about what is there, but rumors abound. Some even think it houses aliens and UFOs. Discover the secrets of Area 51. Red Rhino Books Nonfiction is the first Hi-Lo children's nonfiction series at a first-grade reading level for students in grades 4–7. Visually appealing fullcolor photographs and illustrations—along with fun fact boxes—keep these books flowing. Also includes prereading comprehension questions along with a 20-word glossary for further reading support.