2.5 stars (first one of the series I read) 
 I agree with a lot of thing that were already mentioned. I was ready to make it a 3.5 stars until I learned the reason for they break-up. 
 The D/s element was predictable. A lot of books were perso A is self-destructive and perso B fell the need to protect him end-up with this dynamic. Was not surprise that it's the case for this one. It's a well used cliche. 
 Was not surprise too for the brother.