The Truth of Valor

Former Marine Gunnery Sergeant Torin Kerr is attempting to build a new life with salvage operator Craig Ryder on his ship, the "Promise." Turns out civilian life is a lot rougher than she'd imagined-salvage operators are losing both cargo and lives to pirates. And when they attack the "Promise," Craig is taken prisoner and Torin is left for dead. 
When Torin finds out why the pirates needed Craig, she calls in the Marines to get him back-and to stop the pirates from changing the balance of power in known space. Book 5.