Book 4 of the Kingmaker Chronicles -

The queen has been cursed, and no one knows who’s behind the plot to threaten the realm’s fragile peace. Desperate to help, Jocasta hatches a plan to find Circe’s Garden, a fabled island where she hopes to discover an antidote. But she can’t do it alone. She needs the strong arm and unflinching bravery of the warrior she’s loved since childhood—her brother’s right-hand-man and captain of the guard, Flynn of Sinta.

Together they can do the impossible. Yet with treachery brewing on Mount Olympus, one thing is clear: Thalyria and its new royals are still pawns in an epic game of power—one that might end in a War of Gods.