The wake up : a novel / Catherine Ryan Hyde.

Enhanced descriptions from Syndetics:

From New York Times bestselling author Catherine Ryan Hyde comes an emotional novel of how one man's life changes forever when he rediscovers his ability to feel the pain of others.

Something has been asleep in forty-year-old cattle rancher Aiden Delacorte for a long time. It all comes back in a rush during a hunting trip, when he's suddenly attuned to the animals around him, feeling their pain and fear as if it were his own. But the newfound sensitivity of Aiden's "wake up" has its price. He can no longer sleepwalk through life, holding everyone at arm's length. As he struggles to cope with a trait he's buried since childhood, Aiden falls in love with Gwen, a single mother whose young son bears a burden of his own.

Sullen and broken from his experiences with an abusive father, Milo has turned to acting out in violent and rebellious ways. Aiden can feel the boy's pain, as well as that of his victims. Now he and Milo must sift through their pasts to find empathy with the innocent as well as the guilty, to come to terms with their deepest fears, and to finally discover the compassionate heart of a family.