The book proceeds to give some general background on the history and use of the Psalms as the prayer book of the Bible. In the main part of the book he presents one possible system of categorizing the Psalms according to their petitions, and also points out that they can be organized according to the petitions of the Lord's Prayer. But the most valuable part of the book, in my opinion, is how he shows us how the Psalms are to be prayed in Christ, of whom the Psalms also testify (Luke 24:44). As Bonhoeffer says, "It is the incarnate Son of God, who has borne every human weakness in his own flesh, who here pours out the heart of all humanity before God, and who stands in our place and prays for us."
This is a fine book for the devotional/prayer life of the Christian.