Paul the Traveller, by Ernle Bradford.
This is a biography of Saint Paul, organized around his three missionary journeys. Very interesting take on life in the first century AD, including the social, political, and religious environments. I found the depiction of the life of the Roman Emperor especially intriguing.
Coming from the perspective of the professional biographer and expert on the ancient world, I found this work interesting and insightful. It moved a little too slow for me at times, but it was worth plowing through.