Rinkitink in Oz (version 3) - L. Frank Baum

Prince Inga of Pingaree and King Rinkitink and their companions have adventures that lead to the land of the Nomes and, eventually, Oz. In this story you meet the surly talking goat BilBil and some evil people who conquer the peaceful island of Pingaree. Since his parents, the king and queen of Pingaree are taken away as slaves along with every other citizen of the kingdom, Prince Inga must somehow find them, defeat the enemy and bring them home. King Rinkitink, a roly-poly and jolly monarch who hates ruling, has run away from his people along with his talking goat and goes along with Inga to have more adventures.