From the beginning, the purpose of the book, to “provide a historical assessment of the global spread of Christianity” with “migration as the central lens,” is clear (1). The brief introduction touches on a variety of historiographical approaches—empire (or “top-down”), whole society, and world Christianity approaches—while ultimately proffering the sociohistorical, or “bottom up,” model (6). The methodology is teased out in the first three chapters of the book, which constitute Part One, “Conceptual Overview.” While there is caution against an anti-institutionalization in the sociohistorical method, this approach centers on three pillars: (1) a focus on groups out of power, (2) fascination with aspects of life outside of politics, and (3) patterns and processes of culture (17). The first chapter provides an overview of human migration, descriptions of its varieties, and the dynamics of migration in the context of empire building—where the story of Christianity begins (40). Chapter Two focuses on the role of religion and globalization in the process of human migration. In contrast to “primal religions,” the “major religions” of Christianity, Islam, Buddhism, Hinduism, Judaism, and Zoroastrianism played the most significant role in the globalization of the ancient world (46). Christianity takes the center stage midway through this chapter, as the “sequential stage model of conversion” (52) raises the questions concerning the nature and extent of societal conversion (67). Missiological paradigms, such as Sanneh's translation, Walls's incarnation, and Bentley's social conversion, take center stage in exploring the nature of Christianity's engagement with culture. The third chapter and final section of Part One focuses on the theology of migration in the biblical account. The framing of this chapter raises questions regarding the historicity of the claims of migration in ancient Israel's history (80). However, the chapter presents a biblical survey of the theme of migration and how migration “dominates” the stories of biblical figures (97). The juxtaposition of Adam's negative migration and the redemptive migration of Abraham establish Hanciles's helpful correlation of migration and divine purpose (106). The discussion of biblical principles on the treatment of foreigners simultaneously evokes contemporary issues as well as builds toward the themes of migration and mission. God's desire was to use Israel's exodus, exile, and foreign population for the broader end of theological inclusion (122). The New Testament—with its mention of Jesus's refugee experience and Paul's missionary journeys—solidifies the theme of divine purpose being accomplished through the varieties of migration.

Part Two constitutes the majority of the book and provides a historical overview of trans-local Christian migration during the first fifteen centuries of the Church. Chapter Four considers the Christianization of the Roman Empire, with a focus on how the Christian focus on the “household of God” was strategically important for the growth of the Church among the paroikoi, or “resident alien” (145). This chapter considers early Christian concepts of group identity and forms of othering in the Roman Empire (167), much like Denise Buell's Why This New Race . Chapter Five focuses on the faith of captives and the “shifting position of individual emperors” (184) and how theological debates affected the spread of Christianity outside of the Roman Empire (188). The central focus is on the Arian ascendance of the Gothic missionary Ulfila and the political tensions with the catholic Roman Empire (208). The Ethiopian embrace of Christianity under Ezana is given an unfortunately small amount of attention in this chapter (190–192), especially considering the role of the Arian controversy. Chapter Six is lamentably called the “Minority Report,” referring to the Persian Christian community that was actually equal in size to the Roman imperial Church. As Hanicles rightly points out, the imperial elevation of Christianity in the Roman Empire resulted in the persecution of Persian Christians (223). The theme of migration is further developed as the declining presence of foreign Christians in the waning years of the Sasanian Dynasty provides further case studies for this study of migration and Christian growth (260). It is a breath of fresh air to see texts such as the Chronicle of Seert and the Acts of the Persian Martyrs mentioned in a broad study of Christianity, which tend to focus primarily on Greek, Latin, and European contexts. It is lamentable that the author deployed pejorative terms with a Western/Chalcedonian bias to refer to the Church of the East or the Miaphysite communities, despite some consideration of the damage of these terms (p234). Given the chapter's focus on Sasanian-era Christianity as part of a book on migration and Christian growth, a suggestion for a future edition would be some discussion on the migration of Christians from Persia into Roman Edessa after the death of Emperor Julian. Chapter Seven challenges the “empire” approach (269) at analyzing the conversion process by highlighting missionary migrants and their centrality in the Christianizing of northern Europe during the Middle Ages. By highlighting the nonmilitaristic intervention of monastic and episcopal figures such as Patrick, Columbanus, and Boniface, Hanciles shifts interpretation of the Christianization of northern Europe away from imperial conquest to the translation work of migrants (311). Chapter Eight explores the spread of Christianity in Asia through Silk Road merchants and missionaries during the Tang Dynasty (seventh–tenth centuries). Despite a concerted effort at contextualizing the Christian faith in Central and East Asia, the migrant status of Christianity in these contexts eventually led to its demise (355). While not indicated in the title, Chapter Nine surveys the “complex interactions between vast migrations, empire building, and the fortunes and fate of Christian communities in Islamic and Mongol domains” (359). Readers are helpfully exposed not only to the migration of well-known Europeans such as Marco Polo and William of Rubruck, but also Christian migrants who went west from the East, such as Rabban Sawma and Mar Yaballaha. Chapter Ten summarizes the book's central critique of the “empire argument” by centering the role of migrants in Christian (420). In sum, Hanciles's text offers a thorough survey of the first fifteen centuries of Christian history, highlighting many understudied historical figures, with a unique focus on migration in the transmission of the Christian message.