The Book of Joel accounts for justice over evil in a form that's unique to the other Old Testament prophets. Unlike the other Books, Joel tells us a story about a terrible plague of locusts that seems to traverse across time. No particular mention of Israel's sins is present in the book, but the consequences of the terrible events described are certainly clear: God will one day wipe out all evil and start creation over. But through this destruction also comes eternal protection for those who believe in Him.
Salvation from the Messianic King is once again prophesied, but this time the Holy Spirit is prophesied to come too, causing seemingly ordinary people to have visions, divine dreams, and be filled with God's Spirit. That's exactly what happened during Pentecost to Jesus' disciples after His death and resurrection, ensuring us that the Day of the Lord is even closer at hand today.