Very dark, please check your trigger warnings. 

The book started out pretty good, basic Stockholm Syndrome stuff. Then there was some action which was cool. And then we get into the fluff and domesticities with a side of smut. At this point, the book was like 3 stars - points docked for the MMC and FMC's character inconsistencies.

But the rating went completely down the rabbit hole at the ending because wtf was that???

It was basically a cheating trope thrown in at the end. It didn't even make sense that the MMC was turned on by this because he would kill if FMC so much as interacted with another man but this is ok??? Hypocritical much??? This is where the meme "I can excuse murder but I draw the line at cheating" VERY MUCH APPLIES. Completely ruined my mood and turned me off the whole book. Wish I didn't bother reading the sequel. Some people might say it's not cheating but it counts.