"[I]t is of great importance to correct the enormous confusion Luther caused by inverting the relation and actually criticizing Christ by means of Paul, the Master by means of a follower." (Kierkegaard, 1855.)
A new book that focuses on Jesus' words on salvation (justification and atonement are by repentance from sin and obedience besides faith, and not from faith alone), pursuing the line of reasoning that led Dietrich Bonhoeffer in Cost of Discipleship (1937) to proclaim Jesus taught a gospel of "costly grace."
6 Seek the Lord while he may be found; call upon him while he is near; 7 let the wicked forsake his way,and the unrighteous man his thoughts; let him return to the Lord, that he may have compassion on him, and to our God, for He will abundantly pardon. (Isaiah 55:6-7)