The Shadow and the Star by Laura Kinsale
Dark, dark and darker but rather than subject the reader to graphic descriptions of
abuse, Kinsale smartly leaves the specifics to the imagination (and mine is apparently
a very grim one). A story in which an unwilling physical attraction to an innocent
young woman leads the hero to suffer even
greater emotional torment, while the heroine who, though uncertain of the source of her
lover's pain, embraces it to absorb into herself creates a near perfect darker romance.
I say "near perfect" because the plot is somewhat thin.
Barnes & Noble