I'm a sucker for a strong female character. Ellen Ripley. Honor Harrington. Ace. But Rimrunners (1989) by C.J.Cherryh features one of the hardest, and most substantial characters I've ever come across in sci-fi.
As the novel opens, Bet Yeager, a former starship engineer/marine is stranded on Thule, a Radiator Springs of a space station made irrelevant by the arrival of faster and longer-haul starships. She is homeless and living hand-to-mouth, refusing to become a stationer by taking what little work is available, instead risking everything to be in line for a job when the next starship arrives.
The next starship turns out to be not a scheduled merchanter but the "spook ship" Loki, on an unspecified priority mission. Yeager seizes the opportunity and takes a place on board but is very much out of the frying pan into the fire - she has to adjust to a brutal and unforgiving below-decks society very different from her past experience, and to choose her friends, allies and bedfellows carefully from crewmates who would see her as enemy if they knew of her past (she is a veteran of the events of Downbelow Station).
Cherryh sets the action almost entirely within the ship, and the focus is on the interpersonal relationships and conflicts between crewmembers. The crew are sexually disinhibited - believable given their lack of privacy or personal boundaries in general. They also have very little idea of their ship's current location at any time, although the novel is punctuated by warnings to brace yourself for rocket burns or take your meds for hyperspace transitions (life on board any C.J.Cherryh starship is frequently painful.) Bet is able to glean only a handful of clues about Loki's mission from the officers - these clues, together with Bet's spacer knowledge, prove crucial when the external situation heats up towards the end, and it is only then that Bet has the opportunity to prove to her crewmates and to herself that she has really switched allegiance.
I've not included a picture today however C.J.Cherryh has posted a sketch of Bet Yeager on her website.