It's not the exact reproduction of the Beauty and the Beast theme as the title suggests. 
 Fia is the hidden beauty sort. Due to a childhood incident, she's got a bad limp and her body has scars at multiple places. 
 Dair's recently returned from a sea voyage, having lost his crew, cousin to the torture of Sassenachs (what the Scots called the English then.). Released only to set an example to the other Scots, he's tormented less by the immense physical injuries and more by the horrific memories of how his cousin Jeannie was raped, tortured and hanged. 
 Quite honestly, both the leads seemed to be on a similar footing as far as conventional physical beauty goes and they both have suffered intense trauma. Why should one be called a beauty and the other a beast is beyond me. 
 The romance is pretty sweet so it balances out some negatives for me.