Themes: Wormholes, Space, Nonfiction, Tween. Explore the science behind space-time and find out if wormholes offer a shortcut through galaxies and even allow humans to travel to a parallel universe and time travel. 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.