First of all let me clarify one thing. PTOLEMY has turned adult games into an art form (I think he could possibly make a living as a professional writer), so I am gonna criticize it as such.
Most of the father-daughter incest games tend to follow the same trend, (possibly set by DMD) - the father has to break through the daughter's inhibition and make her fall for him. This games takes the complete opposite approach, and to a good effect. The daughter is the one taking the decisions, and she is not immature/naive like the daughters from many other games. She knows what she is doing. "Don't worry, dad! I'm not stupid. I'm not trying to be your wife" - it's almost like this game is laughing at the naive storylines of other games.
At some moments this game filled me with disgust, and yet at the same time filled me with sexual excitement. And that is the point - the focus of this game is Lust, not Love. The characters are giving in to their dark desires, the game doesn't try to justify their behavior as being natural/good but portray them as they are. While in other games you are making the MC fuck their daughters and yet at the back of your mind you are thinking it's just a stupid game - in this game it almost feels real. You may not like everything the characters do, but you realize where they're coming from. And here lies the success of a writer, he did not give me what I wanted but rather made me change my perspective and see what he wanted me to see. Kudos to PTOLEMY for his awesome job.
The games main focus is on Kelly - the daughter. My reaction in getting to know this girl - OH MY GOD! What a dangerous girl. I would surely be in trouble if I were to have a daughter like her. She seems to care for her father a lot, but she is not perfect, none of the characters in this game are. The complexity of the characters in this game is one of the things I appreciate most. Moreover the fact that you do not play as any one of them, but rather as an outside observer makes it easier to drive the game in the direction you want. It also makes it possible to take morally questionable decisions without any guilt/remorse - "it's not me who is doing those things, what's the problem

".
However, there are several flaws in this game that I would like to point out. Unlike Kelly, the father doesn't seem to have a strong personality. Maybe at some points, the storyline demands it - yet I don't think being sexually attracted to your daughter implies that you should totally submit to her every wish. Also, I could not appreciate Kelly's friend Darla, she runs around naked in front of her friend and her friend's dad - however shameless she might be, that seems too much - to the point of being unrealistic.
Overall, this game takes incest seriously and weaves a deep and interesting story around it. The sexiness of this game is in the story, much more than it is in the sex scenes/sexual encounters. If you think you can appreciate that, you would love this game, just like me.