Dietrich Bonhoeffer (1906–45) is one of the most influential Protestant theologians of the twentieth century. His death at the hands of the Nazis has made him a modern martyr and an icon of radical Christianity.

Without a doubt, the book that has most changed my life is Dietrich Bonhoeffer's The Cost of Discipleship. It is incredible. I first read it at Bible college and then read it again three years ago. Bonhoeffer writes about cheap grace - how we can make the gospel what people want to hear so that we get a bigger response- and how we must fight against that. As an evangelist, I can sometimes feel the temptation to give a softer message to get more people responding, but actually we need to be true to the message that belongs to God. You can change the style, but don't change the substance.