Jonah is one of the more interesting people in the Bible. He was that most human mixture of strength and weakness: Godly yet bigoted, selfish and mean-spirited.
And yet God seems to say to Jonah, "Come, let us reason together, Jonah. You are concerned about this measly vine which I have destroyed with a worm, and you are so angry about it you could die. And yet I want to save this nation, people and animals, and you seem so unconcerned about them. I want no more controversy with you, Jonah, for I am both sovereign and merciful. You are merciful to this gourd which is as nothing to the people in Niveneh, and yet you are angry that I want to overlook their sins and accept their repentence."
This passage from Jonah tells us of God's concern for the population. The great city is as much His distress as the sparrow. God is a God of peoples as well as persons. His Son wept over Jerusalem, "O Jerusalem, Jerusalem ... how often I have longed to gather your children together,...but you were not willing" (Matthew 23:37). Here Nineveh is willing to repent, and God is willing to forgive.
The Book of Jonah is filled with lessons and warnings. One warning is for us to beware of expectations interfering with our present obligations. Jonah expected God to destroy Nineveh, not realizing that God's plans are flexible. Another lesson is to let God lead rather than give in to our own inclinations. Jonah ran the other way and God still caught up with him, for God does know best. Our direction in duty is God's direction. All benefit when all obey. Nineveh did, and so did Jonah, after God reasoned with him.