It is quite amazing that of all the books that exist on the Protestant Reformation, very few chart the intellectual and theological history as being the primary moving force of the Protestant movement. It is still further disheartening that many books wish to treat the Reformation as if it were some sort of absolute novelty and break with the whole of the medieval Western European tradition. Steven Ozment's brilliant study - winner of the Phillip Schaff Award in 1980 - not only bucks the trend on both of these issues, but even traces relevant facets of cultural history - such as the printing press - as he puts the Protestant Reformation into both context and continuity with the medieval era.
More than half the book is spent detailing the medieval world and various theories that would be of the utmost importance to the Reformers: salvation and certainty of knowledge, in particular. The picture that emerges is one in which the Reformation is, in many ways, the absolutely logical outcome of the major trends in believing and practicing the faith after St. Thomas Aquinas. The harmonious worldview that Aquinas sought to put forth in his synthesis of Aristotle and Catholic revelation is largely rejected after the 14th century (re: after the Black Death, in which nearly 40% of Europe's population died).
It has become popular - and for good reason - to note that the fourteenth and fifteenth centuries have a number of trends that are continuous with the Protestant Reformers, although they are rejected by Roman Catholicism. The conciliar movement is well documented by Ozment, as are the tensions between "mystical" and "scholastic" theology that were commonly spoken of at that time. Popular movements such as the Devotio Moderna, which sought to return the Western Church to her more simple foundations of the ancient Councils, Fathers and the Scriptures are also discussed. Medieval "heretics" such as Jan Huss and John Wycliffe are noted as having little influence, however, upon the Reformers - the one exception being Martin Luther, who seemed to be well conscious of his unintentional continuity with a number of the reforming movements of the 14th and 15th centuries.
As Ozment progresses, he notes the major differences between the various Protestant Reformation movements (note the plural!). For example, whereas Luther's movement was started in a backwoods university with a debate concerning the nature of salvation, the Swiss started their Re-formation with a few rebellious priests defiantly eating sausages during Lent! Minor and radical reformers such as John Knox - whose influence would be felt in the later 16th and early 17th century in England - are also looked at; Knox is particularly interesting because his stance on civil matters is so different from that of Luther and Calvin. In short, Knox believed that if the state would not defend a particular form of the reformation - basically, Knox's version of the Reformation - then Christians could rise up and overthrow the state! Luther advocated martyrdom; Knox advocated rebellion. Luther considered people like Knox to be "fanatics" and reformers such as Knox considered Luther to be a failure. Thus, in the end, we can see that the Protestant Reformation has no single legacy but multiple, incompatible legacies that were incompatible from the very beginning.
Of particular interest are the social changes wrought by the Reformation in family life and sexual morality. Despite their differences, all the Reformers agreed that marriage was not a sacrament (it conveyed nothing of God's grace). The huge movement of monks and nuns breaking their monastic vows and being married (which was considered deeply scandalous at the time); the exponential rise in polygamy throughout Europe (its psychological impact was certainly greater than any long-term cultural change); the advocacy of incompatibility as an acceptable reason for divorce among the Protestants; all of these led to what amounts to a sexual revolution for the time period, and all understandings of modern divorce go back to the Reformation.
The book is well illustrated, with woodcuts in particular, and it serves to place the polemical facets of the Reformation into rather sharp relief. It is interesting to note that Lutherans, for instance, understood themselves to stand in perfect continuity with high medieval saints such as St. Francis of Assisi who is depicted as looking with great consternation at the Roman church from heaven in one of the woodcuts.
This is a thick read. It is a little more than 400 pages, but the pages are all oversized (which helps a good bit with the illustrations) and the subject matter can be quite dense. After all, the Reformers all had Scholastic backgrounds and just as they sought to think against their heritage, they also couldn't help but thinking from inside of it; Protestant theology is just as dense and nuanced as that of the Scholastics that came before them. All who take Reformation studies seriously - whether as a scholar or as an "armchair" historian or theologian - can do no better than to consult this volume for the major and minor trends in high medieval and early Reformation thought.