I am a big fan of Timothy Keller.  I especially like the title of this one.  Here are some highlights from the intro:

“What are the marks of a heart that has been radically changed by the grace of God?  If we trust in Christ, what should our hearts be like?  It is not simply a matter of morally virtuous behaviour.  It is quite possible to do all sorts of morally virtuous things when our hearts are filled with fear, with pride or with a desire for power.  We are talking about hearts that have been changed, at the root, by the grace of God–and what that looks like in real life.”