The majority of the “desert castles” of Greater Syria were built when the region was the centre of the Muslim Empire ruled by the Umayyad dynasty (661–750 ce). While most were constructed ex nihilo, some developed existing late Roman constructions; a small number have also sometimes been dated to the early Abbasid period (after 750 ce). Some can be identified with specific patrons, and these have been the focus of particular scholarly attention. Others are impressive architecturally or decoratively and so have been discussed extensively for these reasons. However, the majority have left fewer traces and are the subject of concomitantly fewer analyses. All present significant challenges of classification and interpretation. Indeed, the extent to which these buildings constitute a distinct group at all remains contentious, and there have been various efforts to classify them and to explain their functions.

Genequand's title indicates his own approach to classification: he labels his corpus of 38 separate sites as “aristocratic establishments” (établissements aristocratiques), arguing that this term unites an otherwise fairly disparate group: each comprises “a scattering of different buildings and structures”, built by a member of “the elite” and usually proximate to, but removed from, an existing centre. Genequand further divides the corpus into those with a palace (i.e. more luxurious and with an audience-hall) and those that are simply residences. In line with the work of Alastair Northedge, he also considers the distinction between aristocratic establishments and “new towns” – rural centres dominated by their residence and agricultural functions on the one hand, and foundations with sizeable residential quarters for larger numbers on the other.

The book is in two parts. Part 1 presents a detailed discussion of the evidence for early Islamic elite building in the “Palmyrène”, a region centred on the oasis town of Palmyra and comprising the chain of hills that extend the Anti-Lebanon about 300 kilometres to the north-east, towards Raqqa and Deir al-Zur, as well as the steppes to their south. Part 2 comprises three longer chapters that take in a wider Near East, defined by the author as comprising the western half of the Fertile Crescent, and so the whole region in which such Umayyad-era “desert castles” have been found: modern Jordan, Israel, Palestine, Lebanon and Syria (with one example in Iraq's far north-west and another in northern Saudi Arabia).

Part 1 looks at three sites in particular: the city of Palmyra itself (chapter 5), the elite residence at al-Bakhrā', 21 kilometres to the south of the city (chapter 6), and the substantial development at Qaṣr al-Ḥayr al-Sharqī, 110 kilometres to its east-north-east (chapter 7). Chapter 8 then surveys other elite establishments in the region: Qaṣr al-Ḥayr al-Gharbī, Qudaym, al-Qunayya/Khirbat al-Rashīdiyya, Rasm al-Shaʿar, Qaṣr al-Ṣwāb and some others for which dating and attribution are less certain. These chapters are preceded by one on the Palmyrène's geography (chapter 2) and two on the region in late Roman times and its conquest by the Arabians (chapters 3 and 4).

Part 1 concludes that the coming of Islam marks a significant discontinuity in elite rural settlement in the Syrian steppes; for all that there were some precedents in the settlements of Roman federates in the sixth century, the majority of foundations in the Islamic Palmyrène were new, reflecting changed political and economic conditions. Contrary to received opinion only two were developed on pre-Islamic sites. The others were founded in Islamic times, and at least 12 kilometres from existing establishments – a sort of “mesh”, asserting the presence of new elites in the steppes. Palmyra itself, Genequand suggests, flourished – most likely as a commercial centre at the heart of the territory of Kalb – the tribe who were the Umayyads' close allies. Its economy, he tentatively suggests, was part of a northern Syrian regional system, with only certain specific products showing more distant connections, especially to Iraq and the Ḥijāz.

In Part 2, Genequand expands his scope to include all the aristocratic establishments of Umayyad Greater Syria. He begins with typology, and chapter 10 assesses the component elements of all 38 sites: palaces and residences, mosques, baths, “service buildings”, houses, irrigation and industrial infrastructure and unidentified elements. These are the basis for an attempt at a further subdivision of the broad categories of palaces and residences, alongside the separate category of the new town. In chapter 11, Genequand turns to the economic aspects of the settlements, suggesting that in many cases (somewhere between 21 and 28 of the 38 sites) agriculture was a very significant part of their function, with irrigation works often making crop production possible in otherwise inhospitable conditions. This economic function is connected, following Cahen and Kennedy, to the property law and tax regime of the Islamic state, in which land grants of “unoccupied land” were subject only to the ʿushr or tithe tax, and not to the kharāj, or land tax, and were therefore particularly attractive to their recipients as potential sources of income.

The final chapter of part 2 (chapter 12) assesses the various explanations for the “desert castles” and proposes a hierarchy of three motives for their construction. First, many had a primarily political role in maintaining the links between the ruling elite and the tribes of the Syrian steppes upon whom the military power of the Umayyad Empire depended. Second, in line with the conclusions of chapter 11, the majority clearly had a significant – and sometimes primary – economic function; finally (the criterion for the inclusion of sites in the first place), all also served a residential function, as principal or secondary residences for the elites of Umayyad Syria.

These conclusions build effectively on the work of many earlier scholars, notably Grabar, Gaube, Helms and Sauvaget. As Genequand himself observes, the work remains “a first presentation and a state-of-the-field survey on the Umayyad Palmyrène” as well as “a tentative interpretation of the formal and functional aspects of the Umayyad aristocratic establishments”. It is indeed very much a work in two parts – first on the Palmyrène and then on the whole phenomenon of the desert castle. This may reflect its origins as a doctoral dissertation. However, in both parts, a strong case is made for assessing the desert castles as part of the wider settlement patterns of Greater Syria, with a particular eye to their political and economic functions. Furthermore, the book is an excellent resource, with 391 black-and-white and colour maps and images, and five tables.