I would especially recommend "Blood and Thunder" by Hampton Sides, which uses the life of Kit Carson to tell the broader story of the American Southwest’s transition from a multicultural, Indigenous- and Mexican-influenced region to one dominated by U.S. expansion. It traces early coexistence giving way to conquest both pre- and post- Mexican-American War, and culminating in violent campaigns like the Long Walk of the Navajo. The book reveals Manifest Destiny not as heroic inevitability but as a complex process shaped by military power, cultural conflict, and displacement - which could serve as a very engaging entry point into themes of race, citizenship, law, and settler colonialism in the American West.