Recalling his early days as explorer and entrepreneur, a Colombian president, Rafael Reyes, commented in his memoirs that around the mid-1870s, when he and his brothers settled in the Putumayo in search of cinchona trees for the manufacture of quinine, the region was for most Colombians a virtual terra incognita inhabited by monsters and terrifying beasts no different from those populating the uncharted seas and lands of Columbus’ voyages. Reyes’ observation, together with the account of his explorations and commercial ventures in the Putumayo, holds a special significance in the country's history. On the one hand, these explorations and ventures signalled the opening up of the Putumayo to periodic waves of colonisation from the interior provinces of the country, a phenomenon largely associated with the region's boom-and-bust economic cycles, from quinine and rubber in the late nineteenth and early twentieth centuries to coca and mining from the 1980s and 2000s onwards. On the other hand, and no less importantly, Reyes’ writings pioneered a rich literary tradition that extends to the present and through which the Putumayo has been conceived, imagined and re-imagined across cultures and through time.

Colombia's Forgotten Frontier is concerned with this literary tradition or, as the title of the book indicates, with the literary geography of the Colombian Putumayo. Although ‘Putumayo’ is the name of a department located in the south-west of the country, the geographical scope of the book is considerably larger and includes areas of neighbouring departments and countries, together with the long and meandering Putumayo River. This distinction is important, since Wylie's work is focused not so much on a clearly delimited territory as on a number of landmark historical events and places unevenly spread across a large region. Some of these events include the background and unfolding of the violence linked to the rubber boom, the Colombia–Peru war of 1932–3, and the more recent conflict, from the 1980s onwards, between government, guerrilla and paramilitary forces. Through an engaging literary analysis of the ways in which such events and the places where they have occurred have been represented in a wide array of genres (travel writing, novels, war reporting, testimony and journalism, among others), the author skilfully shows how the Putumayo's history and geography have been culturally constructed over time.

A key thread throughout the book, in line with postcolonial scholarship on the representation of the Amazon, is an emphasis on the shifts and continuities in the Putumayo's literary landscape. A noticeable transition in this landscape, as highlighted by Wylie, is that from nineteenth-century Edenic imageries of the selva, which in characters like Reyes are often entangled with nationalistic rhetoric, to Western descent and dystopian narratives found in later Colombian and foreign travellers and writers, such as Alfred Simson, Jules Crévaux, Miguel Triana, Roger Casement, José Eustasio Rivera and César Uribe Piedrahita. Although the literary styles and motifs of these authors vary substantially from one to another, Wylie effectively shows how they invariably converge in portraying the Putumayo as a ‘savage frontier’, a ‘no man's land’ or a ‘green hell’, images that are well known and deeply rooted in colonial constructions of the tropics.

The power and endurance of those images in the Putumayo's literary geography is well emphasised in the opening chapter of the book, which discusses journalistic and human rights accounts around violence and insurgency in the region during the last two decades. These accounts, as argued by Wylie, tend to associate the Putumayo's regular episodes of bloodshed and terror strongly with its geographical isolation, climate and topography. The effect of the pervasive connection between geography and conflict in such accounts, as in the narratives of the rubber era a century earlier, is that they end up normalising violence in a way that it appears as a ‘natural’ feature of the landscape.

In stressing the persistent juxtaposition of a geographical territory with a moral geography in the fictional and non-fictional literary constructions of the Putumayo, Wylie sheds important light on the role played by these constructions in the region's long history of social and political conflict. The most interesting contribution of the book, however, is perhaps its attention to alternative or counter-discourses subverting, contesting or destabilising colonial tropes and nation-centred narratives of the Putumayo. Among these are writings and testimonies from the 1933 war, indigenous and non-indigenous accounts of the hallucinogenic yagé, and popular novels on the recent violence related to oil and drug trafficking. In the first two instances, the author is especially concerned with the Amazonian cosmovisions and geopoetics present in those testimonies and accounts, and how through them the Putumayo emerges no longer as a spatial and social margin, but as a centre with a historical and cultural identity of its own. In the second case, she considers two different novels, written by a US and a Putumayan writer, and shows how, despite their sensationalist styles, they challenge the traditional notion of violence as an endemic feature of the region and instead interpret it as an effect of external or global forces, especially the penetration of extractive capitalism.

While the author effectively illustrates how counter-narratives of and from the Putumayo have subverted or contested hegemonic literary tropes on the region, a discussion of the presence of those same tropes in academic language – or, alternatively, on the porous border between academic and non-academic discourse – is missing from her analysis. Some of these tropes are actually reproduced in the introductory chapter of the book, which provides a general historical and geographical background of the Putumayo based on scholarly literature. A clear example is the association of the Putumayo's past and present history of violence with it being a ‘no man's land’ (pp. 4, 11) or a territory in continual dispute between government forces and illegal armed groups, marked by ‘crime, poverty, prostitution, drug trafficking, and insurgency’ (p. 10), and where people ‘live in a state of terror and intimidation’ (p. 11).

This argument is well established in the academic literature on the Colombian armed conflict, and stems from the prevalent notion that violence has been an inexorable effect of the absence or precarious presence of the state in vast portions of its territory, commonly referred to as ‘internal frontiers’. Much less attention has been paid, however, to the way in which private or non-government actors have been not external but inherent to the process and practices of state-making in these territories and, at a more general level, to the highly heterogeneous character of the country's many ‘frontiers’. Wylie's otherwise insightful analysis would have benefited from a critical discussion of academic discourse as another form of representation within the Putumayo's literary geography. Despite this, Colombia's Forgotten Frontier is a well-researched and readable book that constitutes an important addition to the literary and historical scholarship not only on the Colombian Putumayo, but also on the broader Amazon region.