Andy McNab 
The New Recruit 
Liam Scott Book 1

What if your prank killed your best friend. Could you live with yourself?
You try to forget and move on; you enrol in Army training, you want to make something of your life. The training is tough and it almost breaks you. But you survive; you know you’ll make a good soldier.
Finally, when you’re out in Afghanistan, under enemy fire, you come face-to-face with your best friend’s brother. He still blames you for his brother’s death. You now have more to fear than just enemy soldiers . . .