BTR Zone: Add- To Reading Levels 1 - 5 Perfect for small group instruction geared toward Response to Intervention, BTR Zone: Bridge to Reading motivates reluctant and struggling readers with high-interest nonfiction focused on science, adventure, biography, history, and sports. With scaffolds such as on-page definitions, photographs, illustrations, captions, subheads, and informational graphics, BTR Zone books provide practice with the text features so important to understanding informational text.