Cold Summer by Gwen Cole

[Skyhorse Publishing] Today, he’s a high school dropout with no future. Tomorrow, he’s a soldier in World War II. Kale Jackson has spent years trying to control his time-traveling ability but hasn't had much luck. One day he lives in 1945, fighting in the war as a sharpshooter and helplessly watching soldiers-friends-die. Then the next day, he’s back in the present, where WWII has bled into his modern life in the form of PTSD, straining his relationship with his father and the few friends he has left. Every day it becomes harder to hide his battle wounds, both physical and mental, from the past. When the ex-girl-next-door, Harper, moves back to town, thoughts of what could be if only he had a normal life begin to haunt him. Harper reminds him of the person he was before the PTSD, which helps anchor him to the present. With practice, maybe Kale could remain in the present permanently and never step foot on a battlefield again. Maybe he can have the normal life he craves.