The sequence of the five books of poetry—Job, Psalms, Proverbs, Ecclesiastes, and Song of Songs—in their spiritual significances is excellent and sweet.
Job stresses that God wants man to seek and gain God solely without any other blessings and prosperity, and that God wants man to seek Him for his perfection and not for his integrity. From this we see that God wants man to seek the kind of perfection that is God Himself, not a perfection based on human uprightness and integrity.
Psalms stresses man's seeking and contacting of God through his praises, prayers, and singing with exultation. The way to seek and contact God is to praise Him, to pray to Him, and to sing with exultation.
Proverbs stresses wisdom that man receives of God through his contacting of God and that teaches man how to behave in his human life.
Ecclesiastes stresses the vanity of vanities of all the things under the sun, which is realized by man through the wisdom received from God. The things under the sun are vanity, but the things in the heavens are reality. If you have contacted God and have received wisdom of God, you will see that everything under the sun is a vanity, a chasing of the wind.