On Trans-Saharan Trails is a book on African economic history that speaks to both Africanists and economic historians in general. Lydon portrays the Sahara as a realm connecting the Maghreb to West Africa through networks of trade, faith, and political economies, which places the book in a growing body of connection-oriented scholarship, appreciative of Braudel's magnum opus on the Mediterranean. Lydon successfully reconciles the rich variety in written and oral sources on the trans-Saharan trade, using Arabic-, English-, French-, and Spanish-language sources and informants. She rightly points to the oral basis of Islam and its influence on the scriptured form of Islamic legal praxis, a point well known to Muslim scholars but not always considered by Islamologists and historians who remain based in philology. The trade networks that Lydon describes can be partly traced through contracts, legal rulings, correspondence, or external descriptions. But fuller knowledge of the history of the trans-Saharan trade can only be gained through oral histories of the day-to-day practice of caravaneering, of the lineage structures that shaped the trade networks, or of traded goods that no longer exist. The book is refreshing for its exploration of lightly trodden trans-Saharan tracks, such as the involvement of women and the presence of Jewish merchants in Timbuktu.

However, Lydon's work is placed squarely in a growing body of scholarship on Saharan history proving the growth, rather than the decline, in trans-Saharan trade in the nineteenth century. This has already been done for the eastern and central trade roads, but only to a small extend for the trade between West Africa and present-day southern Morocco. The book focuses on the Wad Nun region and its inhabitants, the Tikna: a confederation of cosmopolitan Tashelhit-speaking caravaners and traders. In the long nineteenth century (stretching to 1934 in this area), Spain, France, and Morocco competed for political and economic dominance over an essentially autonomous area, ruled by the Bayruk family of the Tikna confederation. Their trading diaspora, departing from their hometown of Guelmim, stretched into the Senegal basin, via Trarza in present-day Mauritania, to Timbuktu and the oases of present-day Algeria. The Tikna diaspora collaborated with the Awlad bu Siba'i federation and the Jewish community of Guelmim. It is therefore not surprising that, throughout the book, Jewish commercial networks – from the Mediterranean down to Timbuktu – receive special attention. The general growth of trans-Saharan trade in the nineteenth century was influenced by larger geopolitics – Islamic state formation in the western Sudan, French occupation of the Senegalese and Algerian coasts, and the reconstruction of Ottoman power in Libya – as well as by the growing connection with trans-Atlantic and Ottoman trade networks, exchanging cotton and weapons for slaves, gum arabic, ostrich feathers, and paper. The latter allowed for better legal and logistic organization, thus building a ‘paper economy of faith’, which is at the heart of this book.

The essence of Lydon's argument on the ‘paper economy of faith’ is that, in the absence of reliable state authorities in the Sahara enforcing law and order, individual entrepreneurs sought knowledge of Islamic law to regulate their transcontinental trade in what Lydon calls a ‘legal culture’. The legal order was upheld by local religious authorities – qadis and muftis – providing legal services, and enforced by personal faith and social norms within the ‘community of believers’. This regulation and structure of the trading society were put to paper, hence the connection between the increasing availability of paper and the renewed increase in trans-Saharan trade from the eighteenth century onwards. Although a tradition of book purchase and production already existed in the region, the relative mass import of paper in the nineteenth century led to increasing contractual trade and trade administration, facilitating secure transactions and trade growth. This was in part financed by the export of book-binding leather, used in Europe in the ever-expanding book industry, and by the booming trade in gum Arabic, used in Europe in (book-binding) glues, and locally in the production of ink. Thus, West Africa and the Sahara were integral parts of a global production of literature, further connecting traders and communities worldwide. Of course, the one snag in this reasoning could be a discrepancy in paper traded in bygone centuries and the volume of paper left to us in the Sahara from the nineteenth century, but this is easily dismissed by the general rise of paper production and use in paper economies worldwide, with which the Saharan trade was simply in line.

This is a rich book. Its scope ranges from a discussion of terminology of directions and the meaning of ‘Sahel’, via a history of tea consumption in the Sahara, to theoretical arguments on early modern trade networks. As a Saharan would say, ‘Lydon has drunk deep’.