Indian Ocean trade networks precede that of the Atlantic World by over a thousand years, yet comparatively, less scholarly attention has been paid to East African links with the Indian Ocean World. Buying Time is thus an important contribution to this area of study. Thomas F. McDow emphasises the interconnectedness of not just the Western Indian Ocean coastal entrepôts, but also the interior of East Africa and Oman. In the 19th century, the global demand for Western Indian Ocean products, such as ivory and dates, coupled with environmental challenges such as drought and floods engendered the mobility of Arabs, Africans and Indians. McDow reconstructs the movements and connections of these Western Indian Ocean actors during that time. These movements of people, he argues, were crucial in the development of the Western Indian Ocean world in the 19th century.

McDow utilises previously unexamined Arabic transaction documents such as business contracts, mortgages and promissory notes from the Zanzibar archives to illustrate how time, debt, mobility and kinship networks linked traders from extensive regions of the Western Indian Ocean and facilitated trade. He also uses genealogies to demonstrate the diversity of the people involved in the business transactions, including Arab elites, women, freed slaves and Indian merchants.

Western Indian Ocean movements enabled people to temporarily escape wars and environmental disasters in their homelands. In some instances, however, they failed to return and settled permanently in the host nations, often in Zanzibar or the African interior, where they were forced to negotiate new identities. In these instances, kinship ties, marriages and sibling partnerships facilitated their settlements and trading networks, as exemplified by the life and trading activities of prominent slave trader Tippu Tip. These new migrants and manumitted slaves needed access to credit to be able to participate in the Indian Ocean ivory trade. Some sold their properties while others relied on Indian creditors in Zanzibar. In the hinterlands, traders recreated coastal towns and the lucrative ivory trade engendered competition and the militarisation of ruling kingdoms, such as the Baganda and Nyamwezi, thereby transforming the political economy of the interior. In the late 19th century, however, Africans’ mobility was curtailed by the introduction of plantation economies that transformed the status of slaves, and the British antislavery treaties that sought to monitor slavery and bring East African Indians under their imperial control.

McDow's book is a valuable addition to the literature on the Indian Ocean world. First, it is a work of transnational history that links areas of the Western Indian Ocean such as the interior of Oman and Eastern and Central Africa, a link often ignored in historical discussions. This is particularly significant because historical scholarship previously focused on coastal entrepôts at the expense of continental hinterlands. Second, it draws attention to the practice of Islamic manumission that existed prior to the European antislavery treaties and enhances our understanding of Indian Ocean slavery. Freed slaves in the Western Indian Ocean were able to take advantage of their connections through their Arab family ties and access to land and credit to participate in the economy of Oman, Zanzibar and the interior of East Africa. Third, the use of debt, mobility and kinship networks as conceptual frameworks enables McDow to focus on subalterns such as poor migrants, freed slaves and Arabs of lower social status that in the past have not received much attention in Western Indian Ocean scholarship. Last, the study highlights the vital role Zanzibar played in Omani politics, largely through financing political activities.

Although McDow's work is an important contribution to Western Indian Ocean history, the text could benefit from a more robust discussion of local Africans in the interior, in addition to powerful male rulers such as Kabaka Mutesa of the Baganda and Mirambo of the Nyamwezi. African women, for example, seem to get attention only through their relationships with their Arab husbands or masters. Nonetheless, the book's Western Indian Ocean scope and accessible writing style make it an important text for World and African History courses.