Unlike a lot of other reviewers, I wouldn't call it a dark romance. I would call it a tragic romance.
Ultimately, there is a happy ending for the main character.. but I did say it was tragic. So take what you will from that.
I'm currently at Chapter 28. From what I can gather, Blair had a stalker, who abducted her and her boyfriend. Her stalker killed her boyfriend and almost killed her. In the book, there is a dream or memory of Blair's where she's begging the stalker not to hurt her boyfriend, how if he actually loves her he wouldn't hurt her boyfriend, and the stalker says something like “Once I'm done you'll never doubt my love.”
If my understanding is correct, I don't understand Blair's reaction to her “stepbrothers'” behaviour once they decide she's ‘Crew'. For example, when they decide to punish the guy she get's caught making out with, after they had notified everyone that she's off limits. While two of her stepbrothers are punishing the guy (breaking his hands), she's being restrained and demanding they not hurt him. Like, come on! How is this not triggering?