The Killjoy. Anne Fine

Nobody, not even his former wife Margaret, has ever treated Ian Laidlaw in a natural way. Presented with his hideous facial scars, everyone he meets reliably falls back on cast-iron, distant courtesy to hide pity or disgust or shock. But then Alicia Davie, a careless young student, breaks the rules totally by laughing in his face. Alicia goes on to infiltrate the hidden man, exposing the obsessive, destructive passions that lurk beneath his primly cordial manner, never realizing that she is playing with fire...