High Steel — Jack C. Haldeman

No man, Mohawk or white, walks the high steel like John Stranger--the highest steel of all, industrial facilities under construction in orbit above Earth. Conscripted by the megacorps that have supplanted nations, unsure if he will ever see his tribe again, Stranger arouses his superiors' suspicions for maintaining the ancient way. Then he survives the suicide duty they assign him to...survives knowing rather a bit too much about how his masters operate.

What Stranger doesn't know is that an interstellar message has reached Earth: not just via the electromagnetic spectrum , but via other media as well. That his superiors have hold of part of it, and are determined to use him to get the rest. That below him, on an Earth increasingly in crisis, the system is collapsing. That the thunder-beings of his forefathers...have invaded mankind's dreams.