These are quite some volumes, in every sense of the word. Physically each weighs in at around 1.75 kilos, and their respective 957 and 773 pages represent a formidably comprehensive overview of the written sources for the earliest period of Christian–Muslim interaction, between 600 and 900 ce and then between 900 and 1050 ce. Future volumes in the series will survey the periods from 1050 to 1200 and then from 1200 to 1500, all fundamentally focused on the Mediterranean region, and then the plan is in due course to produce a further set of volumes which will provide an overview of relations between Christians and Muslims in a wider range of geographical contexts over the past 500 years.

The first volume consists of a 20-page introduction by the chief editor of the whole series, David Thomas, followed by six survey articles, together making up around 100 pages, in turn followed by short articles, very few (e.g. those on The Apocalypse of Pseudo-Methodius, Theophanes the Confessor, Theodore Abu Qurra, Catholicos Timothy I, Hunayn ibn Ishaq) over ten pages in length, on every author and work relevant to the theme, in any language. The six survey articles investigate “Christians and Christianity in the Qur'an” (Jaakko Hameen-Anttila), “Christians and Christianity in Islamic exegesis” (Claude Gilliot), “Christians and Christianity in the Sira of Muhammad” (Suleiman A. Mourad), “Christians and Christianity in hadith works before 900” (David Cook) and, finally, two articles by David M. Freidenreich which make a particularly interesting pairing, “Muslims in canon law, 650–1000” and “Christians in early and classical Sunni law”.

In the second volume there are three introductory articles at the start, a general introduction to the period by John Tolan, an overview of Muslim regard for Christians and Christianity (which are of course not the same) in this period by David Thomas, and then a longer 50-page article by Nicholas Drocourt on “Christian–Muslim diplomatic relations: an overview of the main sources and themes of encounter” on a slightly longer timescale, namely 600–1000. Each volume then ends with an index of names and works included within it.

The articles on individual authors and their works each outline the biography of the author, including the main sources of information for this, and then the relevant works on Christian–Muslim relations in particular, with a description, assessment of their significance, and details of manuscripts, editions, translations and studies. The result is a formidably comprehensive work of reference which will undoubtedly be the obvious first port of call for anyone wishing to investigate a particular writer or an individual work on different aspects of Christian–Muslim relations from this period. The work is also clearly and beautifully produced, a credit to both editors and publishers, and the financial support of the United Kingdom's Arts and Humanities Research Council in making the project and the publication possible is acknowledged with gratitude by the editor in his foreword. A project of this kind is obviously highly suitable for online publication in future, not least so that newly-discovered works, newly-published editions and studies and other relevant material can be included, and this is evidently planned, which will ensure that the results of the project become as widely available and on as long-term a basis as they deserve.

Overall the volumes build very effectively on the work of R. Caspar and others, who in the early volumes of the Pontifical Institute for Arabic and Islamic Studies' journal Islamochristiana endeavoured to produce a comprehensive bibliography of all the works produced by Muslim authors about Christianity and vice versa. Their work, however, was much more limited, in the sense that it included only authors and titles, whereas the volumes under review contain a vastly greater amount of information about both the biographies of the different writers and the contents of their works. There is a huge amount of material out there, and these volumes succeed admirably in providing a comprehensive and accessible survey of it. Texts alone, of course, provide only a partial explanation of the dynamics of the long and complex relationship between the Christian and Muslim communities, since other social, economic and political factors also play a significant role, but as a first port of call for information about the texts these volumes could hardly be bettered.