The concept of the 'heathen' has served as a persistent, evolving framework for defining American identity and exceptionalism, particularly through the lens of race. Kathryn Gin Lum's historical narrative traces the evolution of this concept from the colonial era to the present, demonstrating how it has been employed in both religious and secular discourses to categorize and differentiate Americans from perceived 'others.' Despite the term 'heathen' falling out of common usage by the early 20th century, Lum argues that the underlying ideas—the notion of a world in need of American intervention and conversion to American ways—have persisted, operating as a 'heathen inheritance' that continues to shape American self-perception and its relationship with the rest of the world.

Heathen has been critically acclaimed, earning prestigious awards such as the Philip Schaff Prize, the American Society of Church History S-USIH Book Award, and the Society for U.S. Intellectual History Merle Curti Award in Intellectual History. Reviewers like Kelefa Sanneh of The New Yorker describe it as a 'fascinating book' that posits the Christian/'heathen' divide as central to American life. Philip Jenkins in The Christian Century praises its 'dazzling range of examples' and its ability to inform readers across historical, literary, and religious topics. Emily Suzanne Clark of S-USIH commends its 'brilliant' and accessible writing style, deeming it essential for scholars of American history and suitable for both graduate and undergraduate classrooms.