Heartless by Anne Elisabeth Stengl (Published by Bethany House, July 1, 2010)
Princess Una of Parumvir has come of age and will soon marry. She dreams of a charming prince, but when her first suitor arrives, he's not what she'd hoped. Prince Aethelbald of mysterious Farthestshore has travelled a great distance to prove his love--and also to bring hushed warnings of danger. A dragon is rumored to be on the hunt and blazing a path of terror.
Una, smitten instead with a more dashing prince, refuses Aethelbald's offer--and ignores his cautions with dire consequences. Soon the Dragon King himself is in Parumvir and Una, in giving her heart away unwisely, finds herself in his sights. Only those courageous enough to risk everything have a hope of fighting off this advancing evil.
I love the classic medieval kingdom type of fantasy novel so this sounds like it will be a good read. And the cover is rather interesting, it is what interested me in the book when I spotted it on Amazon.