Amos: THE LORD ROARS
Amos is a nobody from nowhere. He was a simple shepherd from Tekoa that God called to be his mouthpiece for a people that didn't want to be his people.
As a prophet, Amos was to speak to Israel and remind them of their need to return to the Lord, yet Israel was very wealthy and lived as though they didn't need him. They worshiped God in ways that seemed best to them and were self-indulgent, instead of wanting to actually meet with God in the ways he established. Through Amos we see God speak to a people that closed their ears to his word, so the Lord rises up and roars over his people.
Amos was written during a period in Israel's history where they were experiencing abundant wealth under Jeroboam II, but had no interest in being the people God wanted them to be.