An ambitious narrative and analytical history of Christianity that tracks it from its origins as a small Jewish sect to its spread throughout the world as a philosophy governing a remarkable range of societies, by Diarmaid MacCullough, has been bought by Viking here and by Penguin Press in the U.K. for a reported seven-figure advance. It's to be called Christianity: The First Three Thousand Years, and Michael Millman bought it here from U.K. agent Felicity Bryan for North American rights. MacCullough wrote the recent strong-selling The Reformation: A History.