Once Written in Gilded Blood by K.M. Moronova

In a kingdom built on fragile peace, love may be the most dangerous vow of all... Alira made her choice.

She married the Blood Knight to end the war that had ravaged their kingdoms only to fall irrevocably in love with her once-sworn enemy. Now, she is determined to prove that peace between demigods and demons is possible. But something beneath the surface of their paradise feels wrong.

Kalel would burn the world down to protect his bride, but the past he buried in blood refuses to stay silent. As the threat of war closes in on Devicit, Alira and Kalel find themselves caught between the kingdoms they were born to defend. Together, they must confront truths that could shatter everything they've built.

Because peace is never freely given. And the gods are not finished with them yet.