Corydon and the Fall of Atlantis — Tobias Druitt

In this second book in the Corydon trilogy, trouble has invaded the Island of Monsters once again. The peace-loving Minotaur has been
kidnapped! Signs suggest he's been taken to the city of Atlantis, and so Corydon and his fellow monsters set sail to rescue their friend. Their travels across Poseidon's treacherous waters involve one narrow escape after another -- from the volcanic forge of Hephaistos, and the seductive song of the Sirens, from the licentious lair of Dionysos, and the grasping tentacles of the Kraken -- until at last they reach Atlantis. And Atlantis turns out to be more seductive, monstrous, and volatile than anything they've encountered yet.