Successive chapters focus on different religions. Within each chapter, separately titled sections of one to four pages treat specific topics, in roughly chronological order. The effect of this is somewhat scattershot, but it works well to convey the complex patterns of religious change and interaction. There's no attempt to present a theoretical framework or much of an overarching theme — the closest would be an emphasis on the links between religion and trade.
An introductory chapter covers the origins of the term "silk road" (a late 19th century coinage), the way the geography of the region underpinned a "premodern globalization network", early European explorers and depictions of Central Asia, the connections of religion with trade, the "caravan experience", the Sogdians and their central role in trade, the sociolinguistics of proselytization, the central role of women in cultural transmission, and some of the "historical problems" associated with limited and biased evidence.
A short chapter provides background on Indo-European and Iranian religion, introduces Zoroastrianism, and describes Judaism's encounter with Iranian culture and its history in East and Central Asia.
Turning to Buddhism, Foltz provides a brief account of its origins, surveys its different schools, describes local adaptations in Gandhara and among the Kushans, among the Parthians, in the Tarim Basin, in China and in Tibet, and touches on the relationship with Zoroastrianism, the role of pilgrims, and later movements.
Eventually rejected as heresy by the Byzantines, Nestorian Christianity spread in Iran, among the Sogdians, among the Turks, and in China. Manichaeism was an attempt at universalism which drew from Buddhism, Judaism, Christianity and Zoroastrianism but was perceived as a threat by politically dominant religions, finding state sponsorship only among the Uighurs.
After a brief summary of the early history of Islam, Foltz describes the attempts of Muslim armies to conquer Bactria and Sogdiana and the role of religion in the resistance they faced, then looks at Islam's replacement of Zoroastrianism and Buddhism and its spread among Turkish dynasties, in the Tarim Basin, and in China. He also touches on later Jewish trade networks, the Assassins, and the setback for Islam that came with the advent of the Qara-khitai.
A chapter "Ecumenical Mischief" covers the period of Mongol rule, when different religions vied for support from the khans, but attempts at tolerance often exacerbated tensions and rivalries. There's also quite a bit here on early European embassies to the Mongol court.
And a final chapter describes the end of Nestorian Christianity in Central Asia, the underground survival of Manichaeism in China down to the 17th century, and the further Islamization of the region through a popular Islam spread by Sufi orders.
Covering so much, Foltz is necessarily dependent on secondary sources for most of his material, but finds room for quite a few quotes from contemporary or near-contemporary texts. Religions of the Silk Road is referenced in detail, with twenty pages of endnotes and a fifteen page bibliography. Given its broad scope and likely audience, however, some thematic further reading suggestions would have been a useful inclusion.
Foltz provides a fair bit of general background on the major religions. He devotes two pages to the origins and early history of Buddhism in India, for example, and doesn't assume any previous knowledge at all of Manichaeism. He doesn't go into details of doctrines or practices, but does touch on some basic sociology, clearly envisaging that some readers may have naive ideas about the uniformity of religions. So Religions of the Silk Road makes a good introduction for someone with no background in the study of religion.
It may not, on the other hand, work so well for anyone with no background at all in Central Asian history, perhaps coming from a religious studies background. Without a framework to connect them to, the references to people and places will be intimidatingly dense. It won't help here that there's only one low quality hand-drawn map, which doesn't show most of the places mentioned in the text — and which misplaces Taxila north-west of the Hindu Kush.
This is a minor quibble, however; readers can easily find maps and chronologies and other reference material elsewhere. Religions of the Silk Road should be enjoyed by anyone curious about world religious history.