The God Mars Book Three: The Devil You Are - The God Mars, #3

The God Mars is a pulp-style science fiction series set in a rich world of varied cultures and colorful characters. The series plays out a partially-terraformed Mars, a half-century after a man-made disaster cut thousands of colonists off from Earth, and the fear of a rampant nanotech plague prevented rescue. Left to survive for generations with few resources, the various groups develop unique new cultures at different levels of technology, ranging from the primitive to the frighteningly advanced.
And all fear the return of their home planet, because they believe Earth intentionally tried to annihilate them, and will do so again. In Book Three: The Devil You Are, the peoples of Mars are caught in an escalating war between an oppressive Earth terrified of potentially infectious nanotechnology, and an apparently invincible enemy who claims to be from a nightmare future caused by that technology.
In the middle of this, Colonel Ram awakens to find that he has been remade into an immortal superhuman in order to try to save all that he holds dear. But those he would help are terrified of what he's become. And he's not the only one of his kind.