In her first book, Christian Slavery: Conversion and Race in the Protestant Atlantic World, Katharine Gerbner explores the ways in which Christianity, specifically Protestantism, contributed to the continuation of slavery in the Protestant Atlantic world and the development of a white racial consciousness among slave owners. According to Gerbner, Christian slave owners initially resisted the idea of their slaves being converted to Christianity out of fear that they would become rebellious and desire independence if they were religious equals with their masters—a position Gerbner refers to as Protestant Supremacy. Over time, Gerbner contends, this emphasis on Christianity as the distinguishing factor between enslaved people and slave owners gradually gave way to focusing on race, specifically whiteness, as that which gave slave owners the right to rule over slaves. However, even this racial designation was still dependent upon religious rhetoric and ideology, leading to a construct that both enabled slaves to be Christians but maintained the mastership of white Protestants—a construct that Gerbner refers to as Protestant Slavery. Gerbner's thesis, while competing with other works exploring similar ideas, still adds nuance to a broader conversation regarding race, religion, and slavery by focusing on Protestant missionaries and slave owners in the north Atlantic and by looking almost exclusively at Quakers, Anglicans, and Moravians. Christian Slavery is also significant in that it emphasizes the conversion of slaves to Protestant Christianity prior to the great revivals of the eighteenth century.

The book is laid out into eight chapters that are relatively brief but dense with information. The flow of the book begins with Gerbner's focus on the ways in which white Christian missionaries worked to convince slaves to convert to Christianity and slave owners to allow this conversion. However, Gerbner quickly moves the narrative to discussions of the slave's perspective in this process. Herein lies Christian Slavery’s most beneficial contribution to the continuing discussion of slavery and religion in the transatlantic world—the use of primary sources from slave populations. Gerbner quotes extensively from the journals of missionaries and slavers who both transcribed and summarized their discussions with slaves over the issue of religion. These discussions reflect that enslaved African understood the significance of Christian rites, but not always in the same way that white Protestants did. This allows for a fascinating discussion on the nature of conversion, and Gerbner does an excellent job of balancing theoretical approaches with primary-source evidence on the process by which African slaves came to see themselves as part of the same Christian communities of which the missionaries and their owners were a part. This was largely achieved by missionaries preaching a message that reconciled Christianity and bondage, drawing at times upon the Christian scriptures themselves to promote a Protestant faith that reconciled both belief and bondage.

Christian Slavery’s contribution to the field of transatlantic mission work to slave populations therefore helps not only to broaden the scope of scholarship about previously under-examined denominations, but also to show that the context of most missionary-based histories can have a tendency to overemphasize the humanitarian efforts of missionaries. Gerbner drives home the fact that a significant portion of early missionaries in the northern Atlantic world were willing to forgo abolitionist impulses (though some were less willing than others) to convince slave owners to allow them to proselytize to their slaves. This led to a wide variety of stances regarding slavery among Moravians, Anglicans, and Quakers—particularly slave owners from these denominations. Some, particularly among the Society of Friends, did move towards more abolitionist tendencies. Others, most notably the Anglicans, actually worked to secure slavery as a legal institution in order to enable the conversion of more African slaves. The unique geography of Atlantic slavery in the Caribbean also meant that both ideas and missionaries often crossed over and wove between both confessional and legal boundaries. Gerbner uses this aspect of Atlantic slavery to compare practices among missionaries in a transnational and inter-confessional context.

Overall, Christian Slavery is rich in its use of historical sources and girded with good use of theory and excellent design. Gerbner is meticulous in the use of citations and the book is enriched by the inclusion of maps to give shape to the many locations encountered throughout the narrative. This same clarity and careful contribution is found also in the treatment of contested terms—especially conversion. Therefore, this is an engaging book not only for scholars of the transatlantic world, slavery, and the seventeenth and eighteenth centuries, but for anyone interested in the concept of conversion in the broadest possible sense.