The Infinite Cage — Keith Laumer

When he awakens in a skid row alley, Adam knows nothing. Not who he is, nor where he's from. Money is a mystery. So are women. All he begins his new life with is a will to survive. But he learns fast: first, how to get away; then how not to have to. In the beginning Adam wants to be friends with us. Before he's through he just might run the human race off its feet...