Writing a comprehensive yet digestible history of Christianity involves at least three obstacles. First, there is the sheer volume of information to be sifted through and synthesized. Second, there is some stiff competition with existing works that cover particular geographical areas. Third, some of these works already approach the book-is-just-too-thick barrier. In 1998 Eerdmans itself published Mark A. Noll's fine but already lengthy A History of Christianity in the United States and Canada, for example. A world history would seem to call for an even wordier product, yet a longer tome would likely alienate all but scholarly readers deeply committed to the subject. So the challenge is …