Redemption Ark by Alastair Reynolds

In the second book of The Inhibitor Trilogy, Alastair Reynolds pushes the boundaries of science fiction and "confirms his place among the leaders of the hard-science space-opera renaissance" (Publishers Weekly).

Late in the twenty-sixth century, the human race has advanced enough to accidentally trigger the Inhibitors — alien killing machines designed to detect intelligent life and destroy it. The only hope for humanity lies in the recovery of a secret cache of doomsday weapons — and a renegade named Clavain who is determined to find them. But other factions want the weapons for their own purposes — and the weapons themselves have another agenda altogether . . .