A song of wraiths and ruin
(Book)

Series information from publisher's web page.

For Malik, the Solstasia festival is a chance to escape his war-stricken home and start a new life with his sisters in the prosperous desert city of Ziran. But when a vengeful spirit abducts his younger sister, Nadia, as payment to enter the city, Malik strikes a fatal deal--kill Karina, Crown Princess of Ziran, for Nadia's freedom. But Karina has deadly aspirations of her own. Her mother, the Sultana, has been assassinated; her court threatens mutiny; and Solstasia looms like a knife over her neck. Grief-stricken, Karina decides to resurrect her mother through ancient magic ... requiring the beating heart of a king. And she knows just how to obtain one: by offering her hand in marriage to the victor of the Solstasia competition. When Malik rigs his way into the contest, they are set on a heart-pounding course to destroy each other. But as attraction flares between them and ancient evils stir, will they be able to see their tasks to the death?