In the first book of this trilogy, Ship of Smoke and Steel, we met Isoka, an 18-year-old "mage-blood" who's basically Wolverine with (very small, as we are repeatedly reminded) tits who was part of the criminal underworld in her city before she got forced onto the giant ancient ship Soliton, which sails around the world guided by an unknown intelligence collecting mage-bloods and delivering them.... somewhere.
In book two, the "somewhere" turns out to be a city of the ancients, where the survivors of previous Soliton crews have settled into warring factions while a being known as "Prime" periodically sends zombie hordes out to attack them.
We learned in the first book that besides the Well of "Melos," or combat magic, Isoka also possesses the Well of Eddica, the ability to communicate with and control the dead, and which also apparently acts as a kind of electricity for the strange, ancient technology in the Soliton and the city of ziggurats. The worldbuilding here definitely implies some kind of ancient technology, though it coexists with "magic," which mostly acts like psionic/mutant powers.
So Isoka and her crew have to figure out how to end the fighting, defeat Prime, who is an ancient Eddica adept with a zombie army and control of the Matrix, and regain control of the Soliton.
Throughout this book, Isoka is basically a hero, and there's hardly a mention of all the people she murdered back when she was a ward boss.
This book is split between Isoka's POV and that of her younger sister, Tori, who in the first book was just the reason Isoka is in her situation: she became a ward boss so she could provide a sheltered upbringing for her little sister, and now she's being extorted to try to capture the Soliton in order to save her sister.
Tori, of course, is also a mage-blood. Her Well is "Kindre," or mind control magic. Tori, unsurprisingly, knew a lot more about her big sister's activities than Isoka thought, and has been sneaking out to help the poor and downtrodden and also hanging around with a cute aristocrat boy with naive ideals and a desire to help.
Stuff happens, Tori finds herself part of a growing uprising, and she starts using her Kindre power more and more. At first I was really tired of her whining about how she felt "dirty" every time she used it to expose people's feelings or make them do things and how she kept having nightmares about being a "monster."
Then, as the uprising gets more and more serious and Tori is pushed harder, she actually starts using it in earnest. There is a moment near the end where she crosses a moral event horizon as serious as the one Isoka did at the beginning of book one.
So, despite the fact that this was still a very juvenile, very tropey book about 5E Player Characters running a 3rd to 9th level campaign, I am kind of curious to see where the author takes our two morally compromised sisters in the third book. Will there actually be consequences for their evil deeds, or will they get to walk off into the sunset as heroes because they defeated the bad guys?
The sex and romance remains YA and cringey (Isoka is still getting it on with Princess Meroe while oggling enough dudes to remind us she's bi, and really, did we need to hear about a 13-year-old sneaking off to the closet to masturbate?), the action remains D&Dish, the powers remain comic bookish. It's a lightly entertaining YA fantasy epic where I'm still hoping for everyone to die horribly in the end.