The book of Psalms is the prayer book of the Bible.  Seventy-three psalms are attributed to David, 12 to Asaph the musician, 12 to the sons of Korah, two to Solomon, and one each to Heman, Ethan, and Moses.  In the psalms we find not just unparalleled heights of joy, but lament, grief, pain, and enduring affliction.  Psalms is also the psalter - the songbook of the Bible, every word meant to be sung.  The psalms are performative: when we sing them, we are changed and therefore so is the world.  Through these songs we are blessed, protected, convicted, corrected, instructed, undone, relieved, reconciled, restored, and remade in the image of Christ - the Christ who himself sang these songs.  Thomas Watson called Psalm 1 the psalm of psalms.  It introduces the whole book and contains within it the entire scope of the Christian life.