Hosea and Amos were both prophets to the northern kingdom. Hosea picked up the mantle from Amos. John Phillips, in Exploring the Old Testament Book by Book contrasts the two:
Amos thundered out the righteousness of God; Hosea wept out the mercy of God.
Amos took the heathen nations into his prophecy; Hosea limited his utterances to Israel, with occasional reference to Judah.
The style of Amos is clear and lucid, his illustrations drawn from the countryside; Hosea style dispenses short, sharp sentences, his broken home giving him ample illustration to convey the truths that were heavy on his heart.
Hosea is the prophet of outraged love–that love which never lets go; the love that many waters cannot quench; the love that suffers long and is kind.
Amos is the prophet of law, but Hosea had no such unhampered vision of great laws. He was the prophet of love. He tells us that in its deepest aspect, sin breaks not merely God’s law, it breaks His heart.