Paul Nugent's most recent book is, in his own terms, ‘an extended reciprocal comparison with a view to distilling insights that would not have necessarily emerged from a single case study’ (524). The cases compared are the borderlands between Togo and Ghana on the one hand, and those between Senegal and the Gambia on the other. Nugent borrows the term ‘reciprocal comparison’ from Gareth Austin (African Studies Review, 2007), who in turn took it from Kenneth Pomeranz's Great Divergence (Princeton University Press, 2000). For Austin, the comparison at stake was between concepts developed in Africanist scholarship and material gathered elsewhere, which he saw as a prerequisite for avoiding the ‘conceptual Eurocentrism’ that still plagues African Studies. This, he wrote, requires the production of clear narratives and conceptual innovations that would make African history accessible to non-Africanists. Nugent's book is a step in that direction, as it elaborates an original theory of the emergence of (colonial) states, although his concepts remain firmly rooted within European political theory and his conclusion is ultimately pluralist: ‘states only ever exist in the plural because the institutional and ideational permutations are potentially endless’ (12).

Nugent's argument comes in three parts: the boundaries of colonial states were not simply invented at the 1884 Berlin conference. Instead, they were informed by ‘deeper spatial logics’, as colonial states were superposed on already existing political formations, whether these were states, decentralised polities, frontier areas, or something in between. The margins were central to processes of state formation, temporally (‘states were forged in the process of converting frontier zones into colonial borders’, 4, 524), structurally (through the centrality of fiscal policies for processes of state formation), and politically (in terms of the social contract governments could negotiate with their populations, often hinging on the management of trans-border flows of goods and people). States were equally shaped through their interrelations, and the position they occupied vis-à-vis their neighbours. The Gambia and Togo hence emerged as ‘barnacle states’ (538) intrinsically dependent on their larger neighbours, and whose internal fiscal structure was based on a tacit endorsement of smuggling. These structural differences were, in the long run, more important than those more usually ascribed to a contrast between French and British imperial traditions. They continue to influence post-colonial and contemporary states, both through the (fiscal) infrastructure they left behind and the ‘social contract’ that had been gradually negotiated between states and their citizens, making attempts at trans-border unification unpopular on the ground.

Nugent demonstrates this argument in thirteen chapters organised into four parts, and through a sustained comparative history of the two regions under study, ranging from the ‘pre-colonial’ to the 2000s. Given the different kinds of sources available for these periods, and for the different regions treated, the chapters are a little uneven in length, detail given, and register; some are almost exclusively based on state-level statistics and reports, others (more rarely) are attempts at a more localised social history. Although both regions are given equal weight throughout, one cannot but help notice the author's greater familiarity with the Ghana/Togo borderland, and the Anglophone side of things. This is also reflected in the secondary literature cited, which is largely focused on English-language publications. But overall, the diversity and range of source material treated is impressive, and is well held together by the book's strong overall argument.

There can be no doubt that this is a very ambitious project, and one that can be seen as a more general statement about the direction African history ought to take in the future. The book makes important conceptual and theoretical contributions in their own right, that one can imagine being applied universally. This great ambition, however and perhaps inevitably, accounts for what is to my mind the book's principal shortcoming: it is never quite clear who it was written for. It contains the kind of detail one would expect in a local or regional monograph, with a wealth of names, dates, figures and details that are often galling to the non-specialist, but must be precious to anybody familiar with the area. But it also makes broader comparative and conceptual claims that are of value beyond its regional focus, but whose generality could have been spelled out more clearly. These reservations should not detract from the book's stellar qualities, however, and the erudition that underpins it.

It is, in fact, a pleasure to see a book of this kind, one that combines longstanding and meticulous local research with conceptual insights and innovations. All too often, the two are held separate; Paul Nugent's book is proof that one cannot really exist without the other, and that we not only need to think about African borders in different ways, but also question those that dissect our intellectual preconceptions and fields of enquiry – between French and British West Africa, the pre-colonial, colonial and post-colonial, the state and its margins.