The Machine Awakes

Adam Christopher's The Machine Awakes is a far future space opera set in the universe of Burning Dark. In the decades since the human race first made contact with the Spiders—a machine race capable of tearing planets apart—the two groups have fought over interstellar territory. But the war has not been going well for humankind, and with the failure of the Fleet Admiral's secret plan in the Shadow system, the commander is overthrown by a group of hardliners determined to get the war back on track.
When the deposed Fleet Admiral is assassinated, Special Agent Von Kodiak suspects the new guard is eliminating the old. But when the Admiral's replacement is likewise murdered, all bets are off as Kodiak discovers the prime suspect is one of the Fleet's own, a psi-marine and decorated hero—a hero killed in action, months ago, at the same time his twin sister vanished from the Fleet Academy, where she was training to join her brother on the...