The hidden queen / Peter V. Brett.

Humanity thought the war with demonkind was over. Now, after less than a generation to rebuild, the demon corelings have returned with a vengeance. The Spear of Ala—the fortress that stands at the gates of the demon's hive—is the last bastion against the horde, and reports say it may already have fallen. Olive Paper is expected to take the vanguard in the fight. Only an heir of Kaji can wield the artifact that opens the gates of the Spear of Ala, and as Ahmann Jardir's child, Olive seems destined for a role as leader and savior. But Olive does not wish to follow in her father's footsteps any more than she did her mother's. Darin Bales was born with supernatural senses that he struggles to process, and even those who love him believe he can barely take care of himself. Yet to save his mother from the clutches of Alagai Ka, the demon king, Darin will brave anything to mount a rescue. Darin and Olive each strive to walk their own path but find themselves inextricably tied to the legacies of their parents and to a fated confrontation with the demon king and his new hatchling queen. If they fail, humanity may not survive.