Bonhoeffer argues in this book that the Christian is not to believe in "cheap grace", but is called to be a disciple of Christ. Most of the book is spent examining the Sermon on the Mount. Bonhoeffer does an excellent job of highlighting Jesus' words and letting them have their full effect. Christ's words are often uncomfortable and disconcerting, and Bonhoeffer forces the reader to face them full-on. I was very convicted while reading this book of my own lack of obedience to Christ's commands. This is a truly excellent book.