White Assassin (The Zyearth Chronicles)

Trecheon Omnir isn't happy with his life. His motorcycle repair shop barely keeps him afloat, his family has abandoned him, and his experiences in war make it difficult to relate to others. So when his friend and fellow war veteran Neil Black offers him an out, he takes it without question. But Trecheon finds out too late that this "out" is actually an initiation into the world of assassins. Now he must overcome fear, deception, and guilt in order to turn this bad situation into something he can live with and become the profession's first White Assassin.