The Winner's Curse - Marie Rutkoski

As a general's daughter in a vast empire that revels in war and enslaves those it conquers, Kestrel has two choices: she can join the military or get married. Kestrel has other ideas. One day, she is startled to find a kindred spirit in Arin, a young slave up for auction. Following her instinct, Kestrel buys him - and for a sensational price that sets the society gossips talking. It's not long before she has to hide her growing love for Arin. But he, too, has a secret and Kestrel quickly learns that the price she paid for him is much higher than she ever could have imagined. The first novel in a stunning new trilogy, The Winner's Curse is a story of romance, rumours and rebellion, where dirty secrets and careless alliances can be deadly - and everything is at stake.