Gr 4–6—Addressing readers as potential explorers, these intriguing guides integrate information from many subject areas. Interviews with current scientists and explorers are complemented by sketches of people from the past. While presenting adaptations various plants, animals, and people make to survive in extreme conditions, the texts note conservation efforts required to mitigate current environmental threats. Photos and diagrams illustrate specialized terminology such as types of desert landforms. Caves and Mountains create the greatest sense of active participation as readers are introduced to potential dangers such as hypothermia or altitude sickness. "Fact File" boxes with comparative data (e.g., the size of major deserts) at the end of every volume could serve as starting points for developing graphs. Except for Polar Regions, each title suggests ideas for more research. Drawing from biology, anthropology, geology, history, geography, and other disciplines, this series should generate plenty of ideas for further investigation.