Since Ahab has humbled himself before me, I will not bring the evil I had planned during his time. The story of Ahab and Naboth is quite similar to that of David and Uriah, Bathsheba’s husband. In both stories, there is a sin committed because of greed and/or covetousness. In both cases, the Lord sends his messenger the prophet to relay God’s displeasure with the actions undertaken against the “lesser” individual. Just like David will later do, Ahab acknowledges his offence and embarks on repentance. Ahab’s show of remorse is noticed by God who decides to “postpone” until after his death the sentence/punishment that was to be meted out against him. And in both accounts, we are left asking questions about God’s ways while at the same time pondering at the apparent incomprehensibility of God’s ways.
While we might choose to focus on the “actions” of God towards the king and question God’s justice, the real focus is actually on Ahab and his actions. Ahab (as was David, for that matter) is a typical human being, a representation of the human race. He represents the insatiable greed of men and women in every generation. Ahab was not in any need. He had all that he would have wanted in life. But the insatiable vice that is greed led him to want more in the process of which he committed a capital sin. 
Greed is one of the seven deadly sins/vices. It is one of the cancers that is slowly devouring the human society from within, a disease which if not checked can lead to the annihilation of the human race. There is an Ahab in each man and woman who walks the earth. Men and women will always be tempted to amass wealth for themselves, and woe to him or her who dares to stand in the way. That being said, Ahab is also presented to us as a model of humility and of repentance. When the word of God reached his ears, Ahab repented of his sins. He realized the error of his ways and humbled himself before God (of course he had committed a sin and still had to pay for it: he posthumously lost his kingdom). Like Ahab, we are called to be a people who will hear the voice of God calling out to us when we get lost. As the Psalmist says, when we turn to God fully confessing our sins, in compassion, God wipes away our offenses and creates in us a new spirit.