"The Book of the Lion" is a young adult historical fiction novel written by Michael Cadnum. Set in the Middle Ages during the reign of Richard I of England, the story follows the adventures and challenges faced by a young English squire named Edmund as he becomes entangled in the complexities of the Crusades. The novel, published in 2000, is the first installment in Cadnum's Crusader Trilogy and garnered attention with a nomination for the National Book Award for Young People's Literature. Throughout the narrative, readers are taken on a journey that explores themes of morality, loyalty, and the harsh realities of medieval life, all against the backdrop of a turbulent historical period.