Will they solve this medical mystery in time?When Bo Salisbury hurts his ankle playing soccer, doctors think it's a bad bruise. Soon his leg gets worse, and he feels very sick. 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. How can a bite from a pet prairie dog cause a life-threatening...