Solomon wrote three books of the Bible: Proverbs, Ecclesiastes, and Song of Solomon. These books are very strange when you compare them with each other.
Proverbs–everything is rational. There’s a right and a wrong way to do things. The choice between being a fool and being a wise man is up to you.
Ecclesiastes–pretty much everything is stupid.
Song of Solomon–irrational exuberance with life and with another person is awesome, dude!
How in the world does all of this come from one man?
Because it comes from God and there are many sides to God and they all must be taken at one time to make any sense of life.