The genre of Joel is Narrative and Prophetic Oracle. The prophet Joel wrote it around 841-835 B.C. sometime before the fall and exiles of the Northern and Southern Kingdoms. Key personalities are Joel and the people of Judah. Its purpose was to call the Southern Kingdom to repentance or prepare for the coming judgment. Joel describes the locust that inflicts severe damage to everything in their paths, and warns that it is only the beginning of what is to come.
The purpose of the book of Amos was to announce God’s holy judgment on the Kingdom of Israel (the Northern Kingdom), call them to repentance, and to turn from their self-righteous sins and idolatry. God raised up the prophet Amos, as an act of His great mercy to a people who repeatedly shunned and disobeyed Him.