The Winner's Curse by Marie Rutkoski

Set in a world where the Valorian Empire has conquered the Herrani people, the story follows Kestrel, the daughter of a powerful general, who unexpectedly purchases a Herrani slave named Arin at an auction. As Kestrel navigates the intricacies of her society's expectations and her own burgeoning feelings for Arin, she becomes entangled in a web of political intrigue and rebellion. The narrative explores themes of power, loyalty, and the moral complexities of love and war, as Kestrel and Arin's relationship challenges the boundaries of their respective worlds.