This book fills major lacunae in the historiography of the seventh- and eighth-century Arab conquests. Though “intended for a broad audience” (7), it admirably strikes a balance between accessibility and sophistication. Unlike the vast majority of literature which relies predominantly on the post-conquest, ninth- and tenth-century Arabo-Islamic sources, In God's Path makes extensive use of non-Arabic, non-Muslim sources. These possess the dual advantage of being significantly closer to the time of the conquests and of reflecting the views and attitudes of the vanquished, allowing Hoyland to juxtapose their narratives against those of Muslim authors so as to verify or correct the latter's accounts—e.g., the “old idea” that native populations welcomed the Arab invaders (97), or the Arab defeat in 654 at Constantinople left unmentioned in Islamic sources (107–108). These non-Muslim sources also provide further insight into the different ways in which conquered peoples responded to the conquests as well as their participation in the building of Islamic civilization. Importantly, the book situates the conquests within the larger context of the Late Antique world whereby Arabs were not simply outsiders despoiling the Persian and Byzantine Empires, but rather insiders who aspired to conquer and control them. Environmental catastrophes, outbreaks of pandemics, impoverishment, diminishing resources, and imperial exhaustion are accounted for in explicating why nomad tribes, including Turks and Arabs, vied for the riches of the Byzantine and Sasanian Empires. Accordingly, Hoyland demonstrates that the Arab conquests predated the advent of Islam and were only reinvigorated by the rise of the new faith among Arabs.

Comprised of seven chapters, the book offers an analysis of the conquests and their success in chronological order. Beginning with the Late Antique milieu, each chapter delves into a specific episode of the conquests and provides a panoramic view of their unfolding from Arabia, Mesopotamia, and the Levant, stretching out in virtually all directions to North Africa and southern Europe, the Caucasus and the Iranian Plateau, Central Asia and the Indus River Valley. Incorporated seamlessly into this novel presentation is an account of internal changes within the Islamic religion and polity. Hoyland demonstrates how the conquests culminated within three short decades in the Umayyad dynasty's founding of an Arab empire, only to disintegrate into disparate Muslim polities after their overthrow in 750. The book concludes with an in-depth inquiry into the unique role of the conquests in laying the foundation of Islamic civilization.

This polished account of the conquests, however, does not resolve all the tensions and complications that may arise from its use of sources and terms. The author's use of non-Muslim sources, while unquestionably advantageous, is not always accompanied by a critical reading to engage biases and possible inaccuracies. Though Hoyland points out “their preconceptions and biases” (2), iterated in his earlier work (1997), these considerations do not figure in the presentation of sources throughout the book. Moreover, while Hoyland emphasizes the multifarious and changing nature of the Islamic religion, he sometimes refers to “Islam itself” without clarifying what exactly constitutes this reified conception of Islam. He is clearly aware of the tensions created by the use of the term “Islam” as seen in his discussion of “Persianized Islam” and “Arab Islam” vis-à-vis “Gentile Islam” (206, 213ff), as well as his detailed illustration of the process through which Islam became “something of a hybrid religion” (219). Nevertheless, the tension remains, for example, in Hoyland's analysis of the disintegration of the Arab Empire wherein he cites ideological factors and argues that “Islam itself became hostile to an imperial style of government” (211). His use of the term “jihad” involves similar complications. Though In God's Path laudably transcends popular clichés such as the singular roles of Islam and jihad as the ultimate causes of the conquests, it scarcely shows how jihad, a key concept of the book as signaled by its title, underwent changes in different phases of the conquests, particularly when the Arabs chose to professionalize their army rather than rely on tribal warrior bands. The author's hasty two-sentence postscript to address some complexities involved in the idea of jihad is too little, too late (230). There are other issues. For example, Hoyland's claim that “Persia suffered a crisis of confidence and its noble families suspected that the ruling Sasanian dynasty had forfeited the favor of gods” lacks supporting evidence (94), and his assertion that “Muʿawiya fought and killed ʿAli” clearly calls for correction (104). Such issues notwithstanding, In God's Path would still make a wonderful read for the general public, students in Islamic and Middle East studies, and scholars alike.