Rarely do entirely new premodern texts come to light, especially ones lavishly illustrated with numerous maps. But in 2000, a previously unknown manuscript containing a cosmographical treatise and seventeen maps was brought to the attention of Oxford's Emilie Savage-Smith. Referred to as the Book of Curiosities (written between 1020 and 1050, but here in a copy from around 1200), the treatise covers what the authors call both the macrocosm and the microcosm (the skies and the earth), which are seen as mirrors or parallels of each other. Savage-Smith and the manuscript's other main investigator, Yossef Rapoport, have together written an analysis of this work, its contents, and its possible meaning.

The account of the manuscript's discovery and acquisition in chapter 1 reads like an academic thriller, providing a fascinating story of how it was determined to be authentic and important and was purchased by Oxford's Bodleian Library. The number of coincidental factors that combined with the hard work of the authors to make this manuscript available to scholarship, make for a truly remarkable story. But Lost Maps goes further, to provide an analysis of what it can tell us about the state of knowledge in eleventh-century Egypt.

Fatimid Cairo was a centre of learning for both the scholarly and the social elites. The depths of literacy, curiosity about the earth and the cosmos, and patronage of scholarship in the medieval Islamic world come as no surprise. What this particular manuscript shows, however, is the fascinating ways in which, at least in this one treatise, intellectual interest about the world above united with that of the world on earth. The authors argue that this is not simply intellectual interest in the cosmos, but also linked to Ismaili daʿwah, providing itineraries for missionaries to follow and knowledge of the earth, its waters, and its inhabitants. It also unites different intellectual traditions with a focus on navigation to present a comprehensive picture of medieval Islamic maritime knowledge.

Chapter 2 presents the Book's astrological material (reserving technical information about astrology for an appendix). Without being written by or for a professional astrologer, the treatise shows deep commitment to the belief that the celestial spheres influenced events on earth. Stars, comets, and other phenomena are explained, starting from the outermost layers of the cosmos and moving inward/downward through the strata to the earth (moving from the macrocosm to the microcosm), where their effects are seen in human life. Knowledge about these phenomena are taken from Greek, Bedouin, Indian, Coptic, and Persian traditions – showing the comprehensive approach of the author/patron of the manuscript, and the breadth of their learning.

The best known parts of the Book are the illustrated maps that are the subjects of chapters 3–10. The most notable is the rectangular world map, discussed in chapter 3 together with the multiple intellectual and cartographical cultures that influenced its development. Unique in many ways, this map represents at least one first: it features the earliest known graticule, or calibrated scale bar, on any known map. According to the authors, this represents the inheritance of a tradition of maps plotted by coordinates according to latitude and longitude (although this map is itself not plotted). This tradition of mathematical geography is traceable to Ptolemy, whose work the mapmaker clearly knew, and whose approach he combined with the Islamic traditions of the Balkhī school. It may even be the case, as the authors suggest, that the mapmaker worked from an available late antique plotted world map. Overlaid with information from contemporary Islamic cartographical traditions, our mapmaker thus created a hybrid map that Savage-Smith and Rapoport see as bridging late antiquity and Islam in ways that reflect the wider intellectual tradition of translation and adaptation in eleventh-century Cairo. This cartographic hybridity is detailed further in chapter 4, concerning depictions of the Nile (both on the world map and a detail map, one of five river maps in the manuscript).

Chapter 5 turns to the Mediterranean, which was of primary interest to the mapmaker – far more than the lands that surround the sea. The author relied upon navigational manuals to create “the first surviving example of a map looking at the coasts from the sea, rather than the other way around” (p. 130). But they claim that he was not interested in the sea because of commerce, as little information is given about commodities or markets; rather, he focused on military defences. Chapter 6 covers detailed city maps of three Mediterranean ports (Palermo, Mahdia, and Tinnīs), especially their gates, walls, and harbours. What connects the three is their strategic importance for Fatimid power in the central Mediterranean. Thus the authors begin to build their argument that the Book of Curiosities carried above all a religio-political purpose – that of extending Fatimid power and Ismaili doctrine throughout the Mediterranean and beyond.

Chapter 7 pivots to the eastern Mediterranean, which the Book covers thoroughly because it mattered most to Fatimid Cairo. Byzantine islands and coasts are shown in great detail although, as the authors point out, the manuscript was written during a time of relative peace between Byzantine and Fatimid navies: a “unique moment of shared maritime culture” that allowed navigational knowledge to travel across religio-political lines (p. 195). Chapters 8 and 9, however, demonstrate the Book's interest far beyond the Mediterranean – the Indian Ocean coastlines were similarly detailed, as were inland Indus-Ganges river networks. Itineraries to India, China, and along the eastern African coast were linked closely to trade routes, which in turn were connected to areas of Fatimid ambition. This ambition was not simply martial, but also religious – the itineraries could be used by missionaries to spread Ismaili doctrine, according to Savage-Smith and Rapoport.

The Book of Curiosities is a marvel – unique in its maritime orientation, blending of cartographical traditions, global maritime approach, and use of maps without accompanying text to convey information. As Savage-Smith and Rapoport emphasize, work on it continues, and there are many questions unanswered and debates still open. They point out matters of disagreement, from other scholars and even with each other. And readers may not accept all their interpretations, particularly the conclusion that this was intended for use by Ismaili missionaries. So while Lost Maps is not the final word, it is essential reading for anyone interested in pre-modern global maritime communications, the history of cartography, astronomy, and other sciences, and the Islamic (especially Ismaili) worldview. The authors are to be commended for their extraordinary work on this extraordinary manuscript.