What is the author's style in Bonhoeffer: Pastor, Martyr, Prophet, Spy by Eric Metaxas?

This perspective is based on certain fundamental principles - that following and accepting Jesus Christ is the only way to live a good and true earthly life, that Christ was God made manifest on earth, and that study and contemplation of the Bible is the only true, real means of discerning the will of God in everyday life. The faith of both author and his subject contends that that life can only be truly fulfilled through selfless, devoted, faithful seeking of that will and putting it into action, not just through going to church but in crisis, in tranquility, in love and relationship, in confrontation and suffering.