Christopher Ash has written the book(s) that I wanted to exist. Which isn't to say I'm going to stop writing myself, but it's just a pure joy to open up his work and see the very kinds of things I wanted to see. He has three books:
Psalms for You
Teaching Psalms, Vol 1: From Text to Message
Teaching Psalms, Vol 2: From Text to Message
Let me explain what these three books hold, then why it's so good. Psalms for You is a part of a series of books designed to be kind of 'sub-commentary', i.e. a level below a commentary, but suitable for your everyday lay person to read as a kind of easily-digestible study for a book. This volume works through 32 psalms, in pairs, showing how they work, what they say, and how they teach us to pray. Teaching Psalms is two books, part of a series designed to help preachers and teachers teach various parts of the Bible. It contains much that informs Ash's approach in Psalms for you, and that's what I want to look at first.
In the opening of volume 1, Ash makes his case. It's a case I've made before, but he lays it out elegantly and clearly. Firstly, that we need to pray, and in particular we need to pray the psalms because in the psalms we are taught to pray.
The Psalms not only train us to pray; they gradually reshape our affections and our aversions so that we love what we ought to love and hate what we ought to hate. (Teaching Psalms Vol. 1: p.21)
But we have a problem - in fact we can't pray the psalms. We are immediately met with difficulties - much that doesn't apply to us, much that is difficult, imprecations, kingly material, claims to innocence, and so on. Solution? We are to pray the psalms "in Christ". That is for Ash, and myself, the key. The Psalter must be read Christologically, and then Ecclesially, if we are to understand it rightly, and enter into it in prayer. He lays out five considerations for why the psalms are the songs of Jesus:
Christ fulfils the role of David the Anointed King
Christ's full humanity as Jesus the King
The NT testimony about the Psalms and Christ
The work of the Spirit of Christ in inspiring the Psalms
The nature of prayer itself : We pray to the Father, through the Spirit, in and only in the Son.
Ash works this out wonderfully in three initial examples (Pss 3, 16, 63), showing how difficult and unworkable it is to pray these directly to us, or even via David to us, and how it works to interpret these through Jesus and then pray in him. This is the heart of the Christological appropriation of the psalms, and I think (with Ash) that this is the key to how to pray the psalms faithfully and meaningfully. He then goes on to give a bit of a masterclass in both praying the psalms and teaching the psalms. He tackles in particular how we deal with the three problems in the psalms of "I'm not righteous like this" (>> imputed righteousness of Christ), "I don't suffer like this" (we participate in Christ's sufferings as Christ participates in ours), and the ever-problematic imprecations (Ash gives a good, nuanced answer to this, that recognises them as prayers, not curses, sees enemies as primarily God's enemies, hopes for repentance and conversion, while recognising the fitness of God's judgment on the hardened impenitent). He then goes on to trace certain key (redemptive-historical) themes in the psalms, before a final part that gives well-grounded practical advice on teaching the psalms (this is part of a book series designed for teachers of the Bible, after all).
Volume 2 of Teaching Psalms attempts to offer a historical, Christological, Ecclesiological, and finally personally-applicable-prayer comment for every psalm in the Psalter. That's pure gold. I think of this volume as a little handbook to have on standby. I'm using it alongside my evening prayer to quickly orient myself to the psalm for the day and pray it in a more informed, Christocentric, manner. It's so on-target, readily digestibly, and worth every page.
So, really, I cannot recommend these books enough. I'm not saying you should buy one of them or all three, but I am saying that it's not really enough for us to say to people, "Oh, the Psalms are a great resource for prayer and teaching you to pray"; we need to do a little better than that by teaching and training people how to pray the Psalms, and the key to that is recognising them as the songs of Jesus, our great choir leader, and training our minds to enter into prayer with him. In training ourselves to pray the psalms in Christ, we get schooled in Christ's own school of prayer. And in doing that, we learn to pray as Augustine speaks of the Psalms: "Attune your heart to the Psalms... Everything in the Psalter is the mirror of the soul."1
(Attributed, I have not yet found the source in Augustine himself....)