Paul of Tarsus is a pivotal figure in our current read, The Kingdom of the Wicked.
Without judgment, I present the lengthy Wikipedia article on Paul of Tarsus. There are several useful links, among others Authorship of the Pauline epistles, and Paul’s mission and letters from the PBS Frontline series on the earliest Christians.
There is also a recent (2005) and readable biographical novel, just come out in paperback: Apostle Paul by James Cannon.