This was decent. I had a great time at the start as i found MMC Sean absolutely hilarious. I was pleasantly surprised by this being an IR couple without the description of the woman made to feel like some kind of fetish. I would have preferred there to be no racial element in this whatsoever but the part that did include this was handled well which i appreciated. 
Ive rounded up because i enjoyed more of it then i didnt but considering its called Sinner, i did expect Sean to be a little bit more depraved then he was. Being hedonistic didnt really make him bad in my eyes so i wouldve like the book to have leaned into that a bit more. I also wasnt a fine of the teacher element of their coupling. I didnt need him explaining everything he was doing which made it really clinical rather than sexy. 
This was also the case for FMC Zenny. Not a huge fan of a Black girl named Zenobia lol but aside from that she didnt have that much personality. Where Sean had it in spades, Zenny felt rigid with her intelligence and faith so i didnt really know her as much as i did Sean. 
It actually gets quite emotional at times but overall i did enjoy just wouldve liked it darker i think