Revelation Space

Nine hundred thousand years ago, something annihilated the Amarantin civilization just when it was on the verge of discovering space flight. For the human colonists now settling the Amarantin homeworld, what caused the species' destruction is of little more than academic interest. Even after colonists discover an almost perfectly preserved city on the planet, only the archaeological community seems interested. But one scientist, Dan Sylveste, is convinced that solving the Amarantin riddle is vital to the survival of humanity.
Desperate to get at the truth - but with few resources - Sylveste forges a dangerous alliance with the crew of the starship Nostalgia for Infinity. Walking weapons, the ship's cyborg crew could easily become a very real danger to Sylveste's life - but they could also be his only hope to find the answer he so zealously seeks.
As Sylveste closes in on the secret, he learns that one of the cyborgs was sent to kill him. Because the Amarantin were destroyed for a reason - and if that reason is uncovered, the universe - and reality itself - could be irrevocably altered.