Marque and Reprisal — Elizabeth Moon

Though the exciting military career she hoped for never materialized, Ky Vatta still sees plenty of combat. An unknown adversary has launched a full-throttle offensive against Vatta Transport Ltd., Ky's father's interstellar shipping empire -- killing most of Ky's family. Fighting for her very survival, Ky is determined to avenge her family's deaths.

Teaming up with a band of stranded mercenaries, her black-sheep cousin Stella, and Stella's roguish ex-lover, Ky struggles to penetrate the tangled web of political intrigue that surrounds the attacks. Amid suspicion and deception, she is prepared to take whatever measures are necessary to ensure that Vatta stays in business. What she's not prepared for is the shocking truth behind the terror -- and a confrontation with murderous treachery....