I think the blurb sets up a bad set of expectations. "Lesbian necromancers in space" makes it seem like a Sci-Fi/Fantasy LGBT+ romance novel. Instead you get a mystery in a setting that is only technically science-fantasy with a vague romance side plot.
The ending isn't happy, that is for sure.
That was the spec sheet provided by the company, but without any backing info, testing, or engineering expertise. The more digging people have done on this submarine, the more of an absolute shit show it is.