A Curse of Queens by Amanda Bouchet 

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… Read more.