When God saw what they did and how they turned from their evil ways, he had compassion and did not bring upon them the destruction he had threatened.
What a picture of a merciful God in that He forgave the people of Nineveh when they repented. That same radical forgiveness is available for us as well. No matter how bad the things we have done seem, God will accept our repentance and spare us His wrath. Not only did God give Jonah a second chance in this chapter but He also gave the Ninevites another chance and they accepted. If you are looking for a second chance (or maybe a third, fourth, etc.) God is waiting!