Jonah to Amos
Judgment determined.
Mercy
Jonah goes to Nineveh, they listen to him, repent and God does not overthrow the city as he had threatened. In contrast, Amos opens with a message for a number of places where God says he will not turn away from punishing (as he did with Nineveh).
God turned his anger away from Nineveh, but Damascus and the other places in the list at the beginning of Amos are told that God will not "turn away their punishment." Why would Amos have this odd phraseology? Do people think God won't follow through? If they've just read Jonah, the preceeding book, they might think so. After all, God did stand down when the people of Nineveh repented. Given the way he softened towards Nineveh, in fairness, he is forced to say, explicitly, that the results will not be the same this time.
Call
When Jonah heard the call to go warn Nineveh he fled in the opposit direction. Amos, however, just went when called.
Jesus says a prophet is without honor in their home town. Jonah, fortunately, wasn't called to his home town, but to Nineveh, essentially a group of strangers. Amos on the other hand is called to go warn his neighbors, Israel. Nineveh hears Jonah, the stranger, but Israel does not hear Amos. Despite having the harder assignment due to the "home town" principle, Amos goes.
Secrets
Jonah had a reason to run, though. He knew that God would relent in the end and he would look like a false prophet. Imagine, go deliver this message so they will repent and I don't have to destroy them. God gets what he wants, the people are not destroyed and have a better quality of life for their repentance and Jonah, well, he looks false to those who don't understand what happened. No wonder he goes off and sits alone on a distant hill.
Jonah knew God was going to show compassion, so he didn't want to go. He was more concerned with his appearance or what they might to do him if they thought he was a false prophet then saving Nineveh from destruction. Amos says God does nothing without first revealing his secrets to his servants the prophets. Jonah was savvy to what God was doing, he knew the secret that God's threat to destroy Nineveh was designed to bring repentance and would not happen. He runs to Tarshish to avoid the whole thing, but God causes storms and whales and humbling circumstances to bring Jonah back to the original call. As Amos says, Master has spoken, who can but prophesy. Even fleeing to Tarshish doesn't stop the reluctant prophet from delivering God's message.