Surveys of the history of the Reformation appear at fairly regular intervals. It is one of historical scholarship's minor industries. In this case, however, Hans J. Hillerbrand, a recognised master of the history of the Protestant Reformation, has produced a unique synthesis and interpretation. He believes that there definitely was a Reformation although it did not reform the Church so much as divided it. For him the process began with Martin Luther's dispute over indulgences. That incident was transformed first into a major controversy and finally into a movement. Although Hillerbrand is no advocate of the ‘great man’ view of history, he does consider Martin Luther's protest to be the unique spark that started the Reformation. In his view, the Reformation was not the inevitable result of a group of social, economic, political and intellectual causes or the consequence of a corrupt medieval Church. Instead, a unique set of circumstances allowed the contingency of the series of events that ultimately brought about the division of western Christianity. An odd change here or there during the early phase of the Luther controversy would have profoundly changed the outcome. Because he takes this contingent view, Hillerbrand sees the Reformation as a historical episode that started and was centred in the German lands and then spread to the rest of Europe. As a consequence, The division of Christendom focuses on Germany from 1517 to 1555 although it also discusses other countries and regions and follows events through to the end of the sixteenth century. The narrative includes the usual topics such as the English Reformation, sixteenth-century Roman Catholicism and the so-called Radical Reformation. All is informed by Hillerbrand's view of the contingency of history. The division of Christendom presents many fresh and cogent anecdotes. It also provides an excellent discussion of the impact of the Ottoman Turks on political and religious events in the Holy Roman Empire and a somewhat more sympathetic depiction of John Calvin as a man than is normally found in such surveys. This lively and lucid narrative is based on a lifetime of study. Scholars and students will welcome The division of Christendom.