I recently read Eric Metaxas' Bonhoeffer - Pastor, Martyr, Prophet, Spy. I would highly recommend it. The biography reads like a novel, but is still very scholarly. Not only does the author delve into Bonhoeffer's life, but also his theology. He uses numerous journal and other writings of Bonhoeffer and his friends to support his statements. A great and fascinating read that will definitely keep you thinking after you finish.
