This book, by one of the pioneering and leading historians of the Mongol Empire, is a remarkable addition to the increasing body of recent critical studies of the Mongol Empire and moreover, of its impact on, and legacy in, the Islamic world. As with his earlier groundbreaking studies, Peter Jackson brings to the table a meticulous and exhaustive reading of all available sources and a remarkable capacity to consider and synthesize a large mass of detailed evidence. Here, however, also lies the main drawback of Jackson's book. Whereas ideally the book could appeal to readership beyond the narrow confines of Mongol studies or the broader body of medieval Islamic historians, and perhaps even serve as assigned classroom reading, the book is often demanding reading, overburdened by a swath of examples that Jackson painstakingly gathers and considers with great attention. Thus, despite its clear arrangement and subheadings and its unburdened prose, the book's comprehensive nature stands in the way, at several junctures, of even the more experienced reader easily identifying the author's main conclusions. One's impression is that the author is more concerned with pronouncing the final verdict in several of the ongoing debates within the field, and less with opening the discussion to historians of adjunct areas and periods.

At the outset of the book, Jackson presents his two main concerns: the impact of Mongol conquests and rule on the Islamic world, and the character of Mongol rule over Muslim populace. After two introductory chapters – one on the sources and another, a survey of the earlier Muslim–Inner Asian engagements – the book roughly follows a diachronic order. Its first half deals mainly with the period of Mongol expansion and the establishment of the united empire followed by its subsequent dissolution into four separate khanates (up until c. 1260). This is accomplished in chapters 3 (early stages of the Mongol westward expansion, down to 1252), 5 (Hülegü’s campaigns), and 7 (fragmentation and inter-Mongol conflict from the 1250s). In chapter 5, Jackson takes the opportunity to reiterate, albeit slightly modifying and offering additional support for, the conclusions he had reached in his earlier study of the dissolution of the Mongol Empire (1978) that Hülegü was not originally sent to establish his own independent khanate in Iran.

This chronological flow is interrupted by three “thematic” chapters. Chapter 4 is a useful outline of the nascent institutions and overall character of the empire, and 6 explores the issue of devastation and depopulation in the Mongol conquests. Jackson offers a soberer presentation of Mongol violence seeking to balance recent research that has possibly excessively minimized the shock and destruction of the conquests. Chapter 8 briefly visits the issue of transcontinental traffic and cross-Eurasian exchanges that have been expansively studied by Thomas Allsen. Jackson offers a more sceptical and nuanced approach to the idea of a Pax Mongolica, especially considering the intense inter-Mongol warfare and the increased risks in trans-Eurasian travel from the 1260s.

The second half of the book focuses mainly on the second half of the thirteenth century, roughly up until the conversion of the Mongol khans. Chapter 9 examines the fate of local Muslim dynasties and potentates, especially under the Ilkhans. Chapter 10 examines longstanding questions about administration under the still infidel Mongol rule, offering a fresh take even if slightly exasperating in detail, on the shifting balance of power between Mongol amirs and the “civilian” officials, especially considering the process of acculturation. Jackson challenges the conventional distinction between the Mongols as “the men of the sword” and Persian bureaucrats as “the men of the pen”, demonstrating that at different moments, both strata dipped their hands in each, warfare and administration.

Chapter 11 offers an excellent overview of the tension between Mongol and Muslim institutions and practices in taxation, law, and religion. Jackson argues that we replace the notion of Mongol toleration of all religions with a more nuanced historical vision of Mongol policies of pluralism, which makes room for an inconsistent enforcement of steppe traditions on the expense of the freedom of religious practice (slaughtering and ablutions, for example). In this regard, what troubled the Muslims under infidel Mongol rule was not being targeted by the Mongols' religious policies, but that they “now found themselves reduced to parity with Christians and Jews”, who were granted equal privileges in contrast to the Muslim law (315).

The final two chapters explore Mongol Islamization with a focus on the Ilkhanate. Chapter 12 explores motivations for and expressions of conversion, explanations for Muslim success (such as “conceptual affinities” between Islam and Mongol worldviews, 336), and the vectors of conversion, especially Sufi masters. Jackson distinguishes four levels of Mongol relationship with Islam: unexclusive presentation of favour to Muslims and charitable foundations, personal adoption of Muslim practices, enforcement of Muslim law which meant the demotion of rival faiths, and finally active persecution of other religions.

This model, which positions on its one end, the Mongol traditional policy of religious pluralism anchored, according to Jackson, in Chinggis Khan's yasa, and on its other, a full implementation of Sharia, forms also the basis for the final chapter. Jackson examines the conversion of Mongol rulers in the three khanates. Situating convert Mongol rulers on his “Yasa-vs-Sharia scale”, the author assesses the impact of Islam on each individual khan. Taking this scheme a step further, Jackson furthermore suggests that “the avoidance of religious partisanship” in itself might have been “viewed as central to Chinggis Khan's precept” (360), and therefore, when attempts were made to reinstate the yasa on expense of Islamic law, these refer to the reinforcement of the Chinggisid pluralism principle and avoidance of religious partisanship. This model, however, is not without its problems. The reader's impression here is not only that the now-discarded “measuring” of the religious sincerity of the Mongol converts is simply replaced with another form of evaluation: assessing Mongol implementation of the new Muslim faith; but also, that it is difficult to see how this model gives enough leeway to the variance and contingency in Mongol religious affiliation, for which Jackson had fervently advocated earlier in chapter 12. One may, furthermore, question whether the implementation of Muslim law or persecution of non-Muslims too could have addressed other Mongol principles. This chapter in any case ends with the historian Rashid al-Din's assimilative approach to his Mongol overlords and the politics behind his historical vision.

Jackson's book is a monument to the major strides made by historians of the Mongol Empire, a great deal of which has been due to Jackson's own significant contributions. The geographical span of the book is also impressive, with Jackson covering not just the Ilkhanate, but also Mongol rule in the Golden Horde and Chagataid Central Asia, and at several junctures, venturing into Yuan China. The book also testifies to the great deal of work that remains to be done. A comprehensive view of the Mongol impact on the Islamic world needs also to consider the no-less significant intellectual and cultural transformations in the Islamic world under the Mongols, above and beyond the few examples of inter-cultural Eurasian exchange. The book would have also benefited from further attention to questions of gender and female agency, especially in chapter 10, when Jackson discusses Ilkhanid succession, and 12, where he could have also drawn attention to the role of female members in Mongol conversion and acculturation. All this notwithstanding, the book is a remarkable achievement, one that in the long run is sure to become an essential and authoritative reading for all students of the empire.