You cannot go wrong with a Bonhoeffer read - this man is truly an amazing example of God's love and grace. He lived the Word and expressed its value so meaningfully that moves many people in every generation.
I am about half way through the book thus far. This should be a must read for every Christian. Bonhoeffer challenges readers with the applicable truth that GRACE is not GRACE without discipleship. Grace is not cheap but very costly. Discipleship is dependent on Grace and Grace (to be experienced in it's fullness) is dependent on discipleship. He also give one of the best commentaries on the Beattitudes I've ever heard or read. Be challenged in your walk and read the book.