Shan by Viola Rivard

Presented with the possibility of having a true mate, Shan is willing to overlook Harper’s deception—mostly. He’s certain that there’s a wolf inside of her, but bringing it out might be the greatest challenge he’s ever faced. 
As their relationship escalates, Shan tightens his control over Harper.

Between him and the creature threatening to consume her from within, it seems that everyone knows who she is and what she needs, except for her.