Leithart on the wisdom books:
What is wisdom? Follow the canonical progression of wisdom books.
Proverbs: There are two women. Choose Lady Wisdom and reject Lady Folly.
Ecclesiastes: All is hebel. Death looms. Therefore, eat, drink, rejoice in the wife of your youth. Joy in your wife is the way to Lady Wisdom.
Song of Songs: A man rejoices in his bride, eating and drinking a feast of love.
Wisdom is about sex: Proverbs says, Choose the right woman; Ecclesiastes says, Cling to her in defiance of decay; the Song says, Love brings you back to the garden.
Or: Fear of Yahweh is the beginning of wisdom. Joy in defiance of death is wisdom coming to maturity. Fulfilled wisdom is knowing that love is as strong as death.
Or: Proverbs is priestly wisdom, distinguishing wisdom and folly. Ecclesiastes is kingly wisdom, rendering judgments in the midst of darkness. The Song is prophetic wisdom, the hope of future harmony.
Or: Proverbs is past; Ecclesiastes is present; the Song is future.
Or: Proverbs is the Father; Ecclesiastes the Son; the Song is the Song of the Spirit.