Canned heat - Steve Niles

Mark Haggerty was a promising young robotics engineer until his body became fused with an experimental robot suit during a routine testing session. Trapped inside a body that's not his own, and suddenly the unwilling pawn in a deadly struggle between obsessive egos and misguided military forces, Mark's life is forever changed. With his human body consumed more each day by the Cy-bot suit, and the most dangerous elements in the world closing in around him, Mark's only recourse is to keep fighting - until he gets his life back.