One of the leading photographers of our age journeys to Christian communities around the world and, in a stunning book that blends his thoughtful observations with 173 dramatic black-and-white images, produces a magnificent photographic testimony to what it means to be a Christian at the dawn of the third millennium.

Having left his native Iran prior to the Islamic Revolution of 1979, which he covered with great fascination and apprehension, Abbas now devotes much of his energies to probing explorations of religion, seeking to understand why and how religious passion grows. His travels around...