The Swan's Daughter by Roshani Chokshi — book slip

Prince Arris of the Isle of Malys is trapped by a curse that turns royal heirs into trees after marriage, unless they find true love.

His parents announce a tournament of brides, drawing many contenders to Rathe Castle, each with their own motives. Amidst the chaos, Arris meets Demelza, a veritas swan whose song reveals truths.

They strike a deal: her protection in exchange for her song to discern his true love. As they navigate deadly trials and political intrigue, Arris and Demelza must find courage to pursue a life worth living.

For fans of Eva Ibbotson and Ella Enchanted.