Immortal Book by Sue Lynn Tan

Immortal by Sue Lynn Tan is a standalone romantic fantasy novel set in the same universe as her Celestial Kingdom duology. The story follows Liyen, heir to the mortal kingdom of Tianxia, who ascends the throne after her grandfather's death. Determined to free her people from their servitude to the immortals, she forms a precarious alliance with the enigmatic God of War, leading to a tale filled with dangerous secrets, forbidden magic, and a treacherous attraction.