Immortal Killers by Stuart Jaffe

Nathan K — he can hold two souls in his body. If he dies, he loses one yet lives on with the other. As long as he replenishes his second soul, he cannot be killed. Nathan K is immortal.

DYING IS EASY

When Nathan gains his immortality, he learns that living forever is hard. Being immortal throws him into a world of government spies, crime syndicate couriers, and elite assassins. A world in which mankind is second class. A world where one has all eternity to master anything. And Nathan’s not the only one.

But he wants nothing to do with such a dangerous world. He wants to help people, not destroy them. However, trying to escape those who know what he is will prove far more difficult than dying. And it might take forever.