Catherine Higgs has written a marvelous book examining the European dilemma over post-abolition forms of African labor, focusing on the cocoa controversy surrounding Portugal's African colonies. At the story's core, in its evidence and narrative vision, are letters written by Joseph Burtt, hired in 1904 by chocolate manufacturer William Cadbury to investigate whether the Africans who produced his company's cocoa were slave or free. The controversy drew wide attention, and Burtt had counterparts (among them Henry Nevinson and, later, John Harris) who made the story well known, but Chocolate Islands offers something new, partly from Burtt's correspondence and Cadbury's involvement, but also in how Higgs writes a transnational history of ideas about freedom and slavery. Higgs deftly places Burtt's writings in a wider historical and historiographic context, using his descriptions and commentary to connect the different ‘worlds’ that comprised what we now call a global commodity chain. It is a story that links the utopian experimental life of late Victorian England and the hardscrabble farming toil of rural Portugal to the labor experiences of Africans in West, West Central, and Southern Africa; Higgs weaves, with eye-opening success, seemingly disparate threads into a single historical landscape.

Chocolate Islands tracks Burtt's role in the cocoa controversy closely, beginning with his middle-class English background and proceeding through his investigation of African recruitment and laboring life in São Tomé and Principe, Angola, and Mozambique. Two chapters on São Tomé and Principe follow Burtt around the islands as he collected information on working conditions and on how freely African workers got there. The intricate, almost baroque, details of Burtt's itinerary capture his struggle to balance his impressions of horrific conditions with his mission to arrive at a neutral assessment. The analysis wanders slightly, as did Burtt, but captures the texture of island life and the international politics that propelled his voyage. Humanitarian interests claimed the abolitionist mantle and took on commercial enterprises – not only the cocoa growers, but also industrial firms, above all powerful mining concerns in Southern Africa – that argued Africans (or other indigenes) needed a firm European hand to learn the value of labor. In between lay figures such as Cadbury, whose moral sentiments leaned toward the humanitarian but whose economic interest lay in steady access to quality cocoa, and men in the British Foreign Office, pressured by latter-day abolitionists but committed to maintaining South African access to African workers from neighboring Portuguese-ruled Mozambique.

Another pair of chapters chronicles Burtt's extensive and at times harrowing travels in Angola, where he looked for evidence of a clandestine slave trade and whether that trade delivered workers to cocoa fields nearly a thousand miles overseas. The prose brings alive the physical and psychological drama Burtt faced as he sought to untangle the west central African link of the commodity chain. The book is weaker in the chapter on Mozambique, where Burtt tried to determine how freely Mozambican men migrated to South African gold mines. Higgs has less to go on here: Burtt spent only two weeks in Mozambique (in contrast to five months in São Tomé and Principe and a year in Angola), and in delving into southern Africa's recruitment and migration networks, this chapter relies heavily on the secondary literature. Lacking Burtt's travel narrative to drive the story, this chapter may lose the attention of all but the most specialist reader.

One thread Higgs undersells is linked to what was later called ‘the question of slavery’. Clouding the judgment of Burtt, Cadbury, and others was the absence of an international consensus on what constituted slavery in the post-abolition world. In describing the lives of Cadbury Brothers workers outside Birmingham, Portuguese peasants who toiled in olive groves or vineyards, and Africans caught up in labor recruitment regimes for São Tomé roças or South African gold mines, Higgs hints at a fascinating transnational intellectual history. Did workers' human dignity lie in their autonomy – their ability to choose for themselves where to work and for whom – or in the material conditions of their working existence? Higgs notes that Burtt spoke no African languages and had no idea what Africans thought, leaving his capacity to judge painfully crimped. The absence of an African perspective is an unfortunate casualty of the book's unavoidable reliance on Burtt as an interlocutor. For Burtt, ‘the meaning of slavery and freedom in an African context [was] sometimes unfathomable’ (p. 164), and it consequently is for readers of Chocolate Islands as well.

The matter is of enduring significance, as Higgs shows in the epilogue: in the early 2000s, Cadbury and Nestlé faced accusations that they knowingly bought cocoa harvested by enslaved child laborers in Côte d'Ivoire. That children work on cocoa plantations is clear, but just how freely is still a cloudy question, for norms surrounding kin-based claims to labor or how to define the limits of childhood, as well as practices of child-fostering, may make it difficult to draw fixed lines between free and unfree labor. Recapitulating the early twentieth-century debate, connoisseurs of fine chocolate hear unambiguous condemnations from Anti-Slavery International and the International Labor Organization, but knowing what young laborers in West African cocoa fields think is, Higgs tells us, ‘as difficult as it was for Burtt’ (p. 164) more than a century ago.