Hosea, one of the minor prophets active in the 8th cent. BC, suffers more than any other book in the Bible from disputes over its wording, due to differences among text families. Even so, it carries the familiar teachings of the Sinai Covenant concerning sin, judgment, salvation, and the love of God, and the constant tension between steadfast love and the need to purge sin.
Joel focused mostly on Judah and Jerusalem, and was a significant prophet in spite of the shortness of the book. He writes more technically than poetically, and very boldly and to the point.
Amos was a shepherd and an expert on certain kinds of trees, who was given prophetic insight two years before "the earthquake", though there's disagreement over which one this refers to. He was sent to warn the northern kingdom of Israel, whose appearance of prosperity was a thin veneer over corruption and inhumanity.