This bibliography by David Swanson lists a good number of helpful books that inform how we go about crossing the bridges of cultures and build real genuine relationships for the cause of the Gospel of Jesus Christ. These are 4 that he highly recommends:
Disunity in Christ: Uncovering the Hidden Forces That Keep Us Apartby Christena Clevland (2013). The author is a social psychologist and each chapter addresses a different “how” related to social divisions. While Clevland remains hopeful about reconciliation, the book’s particular strength is in showing how entrenched and subtle the sources of our divisions are.
The Christian Imagination: Theology and the Christian Origins ofRaceby Willie James Jennings (2011). Like Carter (see above), Jennings’ book describes in detail the way heretical theology set the stage for the eventual social construct of race. The book traces this neglected (intentionally forgotten?) history by following the lives of a few different key individuals from around the world.