"Shadow Country" is a novel by Peter Matthiessen that explores the life of William H. Bonney, also known as Billy the Kid, a notorious figure from the American West. The book delves into themes of violence, morality, and the complexities of the human experience, set against the backdrop of the harsh landscapes of the American Southwest. The narrative is structured as a trilogy, combining three previously published works: "Killing Mister Watson," "Lost Man's River," and "Bone by Bone." Through rich prose and vivid imagery, Matthiessen examines the historical and cultural significance of the region, while also reflecting on the nature of memory and storytelling.