Surprisingly good.
I won't justify the rape at the beginning because well, it's wrong, even then it's still wrong. But I like how the author makes their relationship a little bit better. We can see the heroine as a concunbine that haven't touched yet. So the father and its daughter-in-law sounds not as disturbing as before. I was speechless when he dare to lay his hands on his son's but it turned out acceptable because the duty stuff (as an excuse), though forced. I'm not into heavy smut but ugh, it is indeed spicy. The plot is not likeable but not bad either. I mean, that's the way it is. Immoral befitting the title. But I'm looking forward to what will happen in the future.
As a side note, I'm a little uncomfortable with the change of balloons from the character's point of view. "I" from one to another. ???? confusing. Sometimes unnoticeable who speaks to whom. The author needs to pay attention to the inner voice of her/his characters.