Shards of honour - Lois McMaster Bujold

Cordelia Naismith is enjoying a baptism of fire. Her first mission is to captain a throwaway warship of the Betan Expeditionary Force on a mission to destroy an entire enemy armada. Discovering deception within deception, treachery within treachery, she is forced into an uneasy peace with her nemesis: Lord Aral Vorkosigan.
Discovering that astrocartography is not the soundest training for a military leader, Cordelia rapidly finds herself the prisoner of the Barrayaran Captain Aral Vorkosigan, also known as 'The Butcher of Komarr'. But the notorious captain is not quite the beast Cordelia was expecting and a grudging respect develops between the two of them. As captor and prisoner on an abandoned outpost planet, the honourable captain and the resolute scientist must rely on each others' trust to survive a trek across dangerous terrain, thus sparking a relationship that shares the struggles of culture and politics between their worlds.