Scholars’ file drawers fill up with drafts, essays, and book ideas that just do not seem to fit within their publishing plans. Typically these pieces stay put, to be discovered only by surviving relatives. This book seemed condemned to that fate, but with some coaxing from colleagues and a friendly publisher, Scott Sunquist, a dean and professor of world Christianity at Fuller Theological Seminary, decided that he had a useful book in the making: an overview of Christianity around the world in the twentieth century. His decision to take up this work again was a good one.

Texts on Christianity's development as a worldwide religion are proliferating just now. Indeed, Sunquist is the co-author (with Dale Irving) of an important two-volume treatment, History of the World Christian Movement (Orbis, 2001, 2012). Others take a more comparative and phenomenological approach, such as Douglas Jacobsen's The World's Christians: Who They Are, Where They Are, and How They Got There (Wiley-Blackwell, 2011). This new offering by Sunquist should compete well with the others because of its brevity, its comprehensive sweep, and its unique thematic style. Indeed, Sunquist argues that the world-roving, integrative approach he takes is necessary for a work on the twentieth century. Christian movements and trends move very fast across the world and can appear almost simultaneously in many nations, so it seems more effective and honest to survey global themes than to focus consecutively on regions.

The author starts with a survey of the world Christian scene in the early twentieth century to provide a baseline for the main theme of the book, a “great reversal” of Christianity's fortunes. Christianity was the main faith of the great imperial powers of Europe and the rising North American nations in 1900, and their church leaders were laying plans to evangelize the whole world. By the end of the twentieth century, however, Christian adherence was declining rapidly in the North Atlantic world. Yet it was growing rapidly in Africa and Asia and being transformed by Pentecostal movements in Latin America. Christianity was becoming a predominantly non-Western religion, and the new Christian heartlands to the global South and East were sending missionaries to Europe and North America.

Sunquist keeps this reversal theme in focus while he surveys five major factors in Christianity's transformation: (1) biographies of influential Christians in each major region; (2) Christianity's encounters with the state, war, and persecution; (3) the fate of Christianity's four major families—the Orthodox churches, Catholics, Protestants, and “Spiritual” churches (Pentecostals and indigenous movements); (4) the faith's mobility via human migration; and (5) Christianity's encounters with other religions.

The main strength of this book is its comprehensive coverage. There is not a major movement, event, or critical moment throughout worldwide Christianity in the 1900s that does not get some mention. With equal dispatch, Sunquist covers both the struggle of European theologians Karl Barth and Dietrich Bonhoeffer to confront the Nazi threat and the rise of prophets and apostles such as William Wade Harris and Simon Kimbangu in colonial Africa. Christianity's encounters with other faiths, most notably Islam, receive major attention, as does the rise of Pentecostalism worldwide and the astonishing reforms of Catholicism arising from Vatican II. Unlike many of the studies of world Christianity, this book treats developments in the West alongside those in the rest of the world, all virtually in the same breath.

Because of the book's short format and thematic approach, however, it seems to be more aimed at broad coverage than at driving a singular thesis or drawing deep meaning from vivid accounts. Virtually everyone and everything of note get mentioned, but their significance and power sometimes seem shortchanged. Even the main thesis—Christianity's “great reversal” in the twentieth century—lacks some nuance. Christianity's demographic weight has shifted toward a non-Western majority, but the relatively new movements look fragile in many places. Meanwhile in the West, where the faith's vitality and pervasive adherence have declined dramatically, revival and renewal movements persist.

It probably is inevitable also, given the demands of covering the world, that errors in fact and questionable interpretations appear. Let me cite just three from the otherwise excellent chapter on migration. The author poses urbanization as a challenge to Christianity, but it has in fact been a tremendous asset. Cities have far greater rates of Christian adherence than rural areas. Likewise, immigration has not been a factor in the dechristianization of Europe, as the author asserts, since most of the new immigrants in Europe are in fact Christians. In the United States, Mexico and Central America do not send most of the immigrants; their share is about 37 percent.

All authors bring a point of view to their work, and even though Sunquist makes every effort to be fair and inclusive, his outlook as a mainline Protestant shows up in a few curious ways. In the chapter on developments among Christianity's major families, he decides that the most important—indeed almost the only—twentieth-century development among Protestants worth knowing is the long series of ecumenical councils and conferences. And in the “Christian lives” biographies section, he decides that among the three most influential or emblematic North American Christians, Letty Russell, a pioneering feminist theologian at Yale, ranks alongside Billy Graham and Martin Luther King, Jr. One might think of several North American women who did much more to shape the faith and their times: how about Dorothy Day? Aimee Semple Mcpherson? Eleanor Roosevelt? To be fair, Sister Aimee and Dorothy Day do at least get mentioned elsewhere in the book.

On balance, however, The Unexpected Christian Century will be a useful introductory text for a course on world Christianity. It ranges broadly, has a hopeful outlook, and conserves reading time for some good supplemental texts. I am glad that the author rescued it from his file drawer.