A Goodreads "YA Best Book of the Month"
An Amazon "Best Book of the Month: Science Fiction & Fantasy"

Zera is a Heartless—the immortal, ageless soldier of a witch. Bound to the witch Nightsinger, Zera longs for freedom. As long as her heart’s captured in a jar and under Nightsinger's control, she must serve the witch unquestioningly…until Nightsinger makes Zera an offer she can’t refuse: a prince's heart in exchange for Zera’s.

Only there’s a vicious catch: if Zera is exposed while she’s infiltrating the court, Nightsinger will destroy her heart.

Crown Prince Lucien d'Malvane hates the royal court as much as they love him—every tutor too afraid to correct him and every girl jockeying for a place at his handsome side. No one can challenge him—until the arrival of Lady Zera. She's inelegant, smart-mouthed, carefree…and out for his blood. Now it’s a game of cat and mouse between a teenaged girl with nothing to lose and a young man who has it all.

Winner takes the loser's heart.

Literally.

The Bring Me Their Hearts series is best enjoyed in order.
Reading Order:
Book #1 Bring Me Their Hearts
Book #2 Find Me Their Bones
Book #3 Send Me Their Souls