A Kingdom of Flesh and Fire: by Jennifer L Armentrout

Poppy's world shatters when she discovers that everything she believed is a lie, including the man she loved. Now, surrounded by enemies, she's forced to confront her true identity and her complicated feelings for Casteel Da'Neer, the seductive Prince of Atlantia.

Though she can't trust him, Casteel is her only hope to find her brother. Their partnership is dangerous, filled with temptation, pleasure, and pain.

As unrest rises in Atlantia, Poppy becomes the key to a war. Dark secrets emerge, and as her powers grow, so do the fears surrounding her, threatening everything.