When Ella Andrews's best friend, Avery, goes missing, she'll do anything to get him back—even follow a strange shadow to another world where the constellations are real-life figures in the sky.Draco, Scorpius, and Serpens have fallen and are destroying the world of Stellaris. And the princess is forcing Ella, Avery, and an army of other kids kidnapped from their world to fight the rogue constellations. But Stellaris isn't meant for humans, and the longer Ella and the others stay, the more they fade into substanceless shadows—a fate worse than death.Can Ella save Stellaris before there's nothing left of her and Avery?