In the 1520s, the emperor Charles v watched helplessly as the confessional orthodoxy of the Holy Roman Empire crumbled away under the weight of Martin Luther's movement. It made him determined that heresy would not spread in his ancestral Netherlandish lands. In 1523, the first Lutheran sympathisers executed anywhere in Europe would be burned at the stake in Brussels. By the middle years of the 1560s, they had been followed by more than 3,000 other Netherlanders.

As Christine Kooi points out in her admirable new synthesis of religious change in the sixteenth-century Low Countries, the early Netherlandish Reformation was marked by violent state repression. While in other regions, such as France, religious change prompted extensive popular violence between confessional groups, most religious violence in the Low Countries was perpetrated by the authorities. The ironical unintended consequence of attempts at eradication of Protestant heresy in the Netherlands was the growth of a large Reformed movement. This was coupled with increasing agitation among Netherlanders against the Habsburg government, which had united the seventeen provinces of the Low Countries by the 1540s under a single dynasty. The eruption of noble and popular unrest in 1566, long seen as the spark of the Dutch Revolt, was directly related to the issue of religious repression. Without the Reformation, there would have been no Dutch Revolt, nor an independent Dutch Republic.

The importance of the Reformation to the political, social and cultural history of the Low Countries in the sixteenth century certainly justifies the appearance of Kooi's book, which is the first English-language synthesis of its kind. The work identifies the origins and beginnings of religious change in the Low Countries in the early sixteenth century, and takes the story to the end of the Twelve Years’ Truce (1621). By this time, a loose conglomeration of diverse provinces had solidified into two distinct political entities, the Dutch Republic and the Habsburg Southern Netherlands, and divergent reformations were intrinsically built into the identities of the two states. The Republic was a Reformed confederation, but with substantial minorities of Catholics, Mennonites and Lutherans; the Habsburg Netherlands was a much more homogenous bulwark of the Catholic Counter-Reformation.

Kooi demonstrates that before the onset of the Reformation, the Low Countries was a distinctly devout region, and not one necessarily more disturbed by calls for religious renewal than elsewhere in Europe. The origins of change can therefore be found more in the strong civic-religious identity that stood at the core of Netherlandish society; the fierce protection of local liberties and freedom of conscience that were championed in the face of Habsburg ‘tyranny’; and the strong commercial and international character of the region. The cities of the Low Countries were linguistic and confessional melting pots, home to sizeable communities of merchants and immigrants, which aided the rapid spread of religious debate. A highly developed print trade further bolstered the communication of religious ideas and the consolidation of rival churches.

Religious change in every denomination is included in Kooi's study: the early Lutheran challenge, the rise of Anabaptism and its transformation into the Mennonites, the building of a Reformed Church and Catholic renewal and reformation. In a bid to be balanced Kooi emphasises the importance of Catholic Counter-Reformation, but it is noteworthy that popular participation and agency, a key part of the Netherlandish reformation in Kooi's telling, is largely missing from the Catholic side of the story until deep into the Dutch Revolt. Before then, efforts of change within the Catholic Church were driven by secular authorities and the church hierarchy, in contrast to religious change in the north. It is also doubtful that it was popular activism that created a dominant Catholic society in the Southern Netherlands by 1620: the political generosity of allowing southern Protestants to leave for the north in the wake of Parma's reconquests seems more influential, coupled with uncompromising treatment of those Protestants who decided to stay behind.

The two key distinguishing aspects that Kooi identifies as critical to Netherlandish reformation, violent repression and the formation of a new republican state, were as much political as religious in nature. The inseparability of religion and politics is emphasised throughout Kooi's book, although she devotes little attention to the political and military events of the Dutch Revolt, which in themselves also stimulated religious change, at a pace that was often faster than desired by most Netherlanders.

This is a book that will prove popular among students, something that I can attest from the reaction of my third-year undergraduates studying the Dutch Republic. Kooi writes in an accessible and concise manner, and has distilled a wealth of detailed, case-study-driven scholarship into one coherent overview. It makes for an ideal point of entry to the study of the Reformation. Occasionally, the relatively short length of the book does work against it. While Kooi rightly emphasises that the Low Countries was an extremely diverse region, and that experiences of religious change differed greatly between towns and provinces, the book cannot delve in any detail into the influence of such diversity on the Reformation. It is impossible to explore every topographical nook in a synthesis such as this, but the absence of many of the seventeen Netherlandish provinces from the index is very striking.

Writing a synthesis is a balancing act, and Kooi mostly balances adeptly. Readers familiar with the Reformation in the Low Countries will find the sweeping breadth welcome, and useful for teaching. Those unfamiliar with the subject will enjoy a highly competent introduction to religious change in a bewilderingly complex region. What both the scholar and the novice will miss at times, however, is a strong argument. The notion that ‘The Reformation in the Low Countries was many things at once’ (p. 188) is not inaccurate, but leaves the reader desiring a more daring voice on the part of the author. It is undeniable, however, that Kooi's book is an achievement, and successfully explains how one European region split inseparably into two confessional halves. As Kooi concludes, the impact of this revolution can still be felt today. It plays a major role in what separates the Netherlands from Belgium, confessionally, culturally and topographically.