A thought on the book of Psalms:
Every book in the Bible has it’s own spirit; it’s own flavour. The author- or in this case, the authors and compilers- moved by the Holy Spirit, assembled this book as a reflection of God’s saving faithfulness to David and to Israel. In doing so, God made it a book for all times and all peoples.
No one book of the Bible shows a complete picture of God as all are written in context of time, circumstance and place. Psalms however may come closest to showing divine acceptance and steadfast love to the sin broken condition of any willing soul determined to move towards the Lord. Psalm’s use by the Lord and in the New Testament shows it’s great healing value of the soul.
In the long view, Psalms uses both David and Israel as intercessory forerunners for the fulfillment of messianic prophecies of the Lord Jesus and the completed Body of Christ as a nation. By doing so, it shows you and I that it’s safe to trust God and how to walk forward in humility and faith.