Phillip Berryman's book insightfully captures the religious goings on of Sao Paolo and Caracas. This book goes a long way towards explaining the interaction between the traditional Catholic ways of religion, the mainline Protestants and the relatively new Pentacostal movements.
Furthermore, Berryman's study serves as a model for the way in which these interactions have taken place in other areas of the world, such as the US, where they are far along, Africa, where they are just beginning and Asia which is somewhere in between.
I would have been interested in more history of these developments, especially how the movements emmigrated from the US, then again, I'm probably one of those overly US centered Americans. :)