Bonhoeffer: Pastor, Martyr, Prophet, Spy by Eric Metaxis. It's one of the best biographies I've ever read and it's on sale for only $9.98 through the end of the month at ChristianAudio.com. It recently was awarded the 2011 Evangelical Christian Publisher's Association Book of the Year. This is a great deal.
Here's the description.
From the New York Times bestselling author of Amazing Grace, this is a groundbreaking biography of Dietrich Bonhoeffer, one of the greatest heroes of the twentieth century, the man who stood up to Hitler. A definitive, deeply moving narrative, Bonhoeffer is a story of moral courage in the face of the monstrous evil that was Nazism.
Bonhoeffer presents a profoundly orthodox Christian theologian whose faith led him to boldly confront the greatest evil of the twentieth century and uncovers never-before-revealed facts, including the story of his passionate romance.