The book of Psalms is a unique collection of poetry which spans and records a full range of human emotion and devotion to God. The Psalter writes of fear, discouragement, horror, joy and gratitude. He also writes about feeling that God has disowned or "left" him, sometimes as a consequence of guilt or human sin.
The Psalms bring a wonderful quality, much needed in the Old Testament. It gives the reader a view into the heart of King David, at various intervals of his life. It also gives the reader something personal, yet universal which covers many years in history; we can relate to many of the same emotions and feelings that he had through reading Psalms.