Richard Allen's book represents what may be the first attempt to fully grapple with the scale of and connections between diverse imperial slave trading operations in the Indian Ocean during the peak of the European capture and sale of Africans. In breadth and accomplishment, this book reminds me of Philip Curtin's 1969 The Atlantic Slave Trade, but the comparison has limits since, to Allen, European slaving operations in the Indian Ocean were unlike those in the Atlantic. More similar is Paul Lovejoy's Transformations in Slavery, insofar as Allen documents the shifting economic, political, and social contexts on all sides of the Indian Ocean and in Europe, chapter-by-chapter and empire-by-empire, and he also examines transformations in enslavement practices and modalities.

Allen seems less interested in bequeathing a Curtinesque magnum opus than in pulling together conflicting or overlapping themes and historiographical issues in Indian Ocean studies that he considers can be better ordered. He seeks to draw attention to the Indian Ocean as an important site for European innovation in government-sponsored and private slaving activities. Central to this is his focus on the “internal” Indian trade rather than the external or Atlantic trade of Indian Ocean origin. He shows how local South Asian economic dynamics shaped the trade in powerful ways that often eclipsed European agendas. Just as Europeans in nascent colonial outposts struggled to navigate shifting local labor demands, and remained hostage to their own prejudices and biases, historians of European Asian empires have too often overlooked or downplayed the coerced nature of the laboring force within those empires' spheres of influence.

Allen estimates that the Indian Ocean trade that was “directly” tied to Europeans constituted about 10 percent of the volume of the Atlantic trade during early modernity (24). This is an important statistic, but for a number of reasons it may prove problematic. For one thing, slave trading in the Indian Ocean has a more complex history than in the Atlantic, and reaches farther back into the past. In fact, as Allen seeks to elevate the significance of the “internal” Indian Ocean trade to counterbalance historical over-attention to coerced labor exiting the market westward, his European periodization may undercut the significance of pre-European trading cycles and practices, and thus skew understanding of later imperial developments.

The paucity of documentary evidence about the idiosyncratic routes and highly speculative trading within the Indian Ocean has long befuddled scholars. Consequently, the history of European trade in this oceanic sphere has been fragmented and unbalanced. Allen's goal is primarily foundational, to establish a base for the future research. While various versions of some of the chapters have been published over several years in different venues, here they are complemented with richer data and brought into conversation. European Slave Trading in the Indian Ocean may well become the go-to source to comprehend the grand contours of the Indian Ocean trade. Future research will hopefully include greater attention to the Portuguese (and possibly Spanish) dimensions of trading in the region, since the Portuguese were the first and likely the last to purchase and transport African slaves in and out of the Indian Ocean area.