John Adams & John Glasby 
When The Gods Came [EPUB ebook] 

Men had fought wars throughout history, but never such a war as the one which destroyed the cities of earth and turned vast areas into badlands, stretches of intense radioactivity where nothing could grow and no one could live. It also produced the deviates, mutants who had warped bodies and strange talents.But there were others who had still stranger talents, mental powers exceeding those of the mutants, and whose bodies did not bear the sign of the deviate. Their origin could not be traced to an atomic war; even they themselves had no idea whence they came.Forced to take part in the abortive war between the Eastern and Western Federations, one man and one man eventually escaped and discovered creatures similar to themselves. But to discover their origin they had to go back five thousand years; and the answer lay not on earth, but somewhere in the stars.