Usually, "grimdark" is a callsign for writing that is meant to be on the cynical but fun side. A story that is led by antiheroes who exist in noir-like fantasy or sci-fi environments more akin to Medieval Grand Theft Auto than anything serious. Indentured Magic is anything but as it deals with the serious subject of human trafficking from a fantasy perspective. I also give props to this work for including charities for dealing with the subject at the end. This is a book dealing with serious subject matter in a serious way, though using a fantasy backdrop. It will not be for everyone and isn't meant to be but is something I encourage readers to check out.
Medea is one of the female students at an Assassin school and she has kinda-sorta failed her last test. She managed to defeat a master in battle but not decisively and not without controversy. This results in her being sent on a mission to investigate a brothel owner who has been enslaving young women. This matter immediately goes to hell as Medea ends up killing the man after he tries to enslave her as a prostitute. This results in her being arrested because the authorities are on the side of the slaver.
From there, Medea finds out that the ring of slavers is far vaster than she expected and there is more at stake than sex. The slave lords are draining the magic of young women, bit by bit, until they are dried up and sold as more traditional sex slaves. Worse, they are charmed through a combination of magic and Stockholm Syndrome in order to make them more compliant slaves. The author draws from real life psychological tactics and the dependence of the captives on their captors in order to makes sure that the situation feels authentic.
The book isn't a very "fun" one and often includes its heroines and other women in extremely sorry states. Surprisingly (and for the better), the book manages to avoid sexual assault for the most part. It's referred to via allusion or through the metaphor of having their magic drained away. Still, the sense of fear and helplessness invoked in this book is tremendous.
I was very intrigued by the magical system presented in the book and how it relates to the society as a whole. The number of women who possess magic is implied to outnumber men or is something that is kept brutally suppressed by individuals who drain it. Its a useful but nonviolent skill that the villains exploit. It's also not terribly well-understood as customers frequently ask for far more than the women being prostituted for sorcery can give. Worse, the slavers "burn out" their subjects rapidly out of their desire to take more than can be regenerated.
The casual misogyny on display is something that will undoubtedly bother many readers but depiction is not condoning. Medea is trying to infiltrate a world where women are commodities and has trouble adjusting to it because she's from a relatively egalitarian school. They are sexist there but not actively monstrous to women as the world of human trafficking is. I was reminded a bit of Stieg Larson in places, though this is more Conan the Barbarian from the perspective of the women he rescues.
Is this a good book? Very much so. It has its flaws like the fact the scenes of helplessness and women struggling against their mind-control are a bit repetitive toward the end. The reader gets what sort of world this is early on and we see many more examples of what utter scumbag the villains are than we really need. I think for mainstream appeal, we should have had a bit more of Medea murdering pimps and slavers. However, that's not what the author was going for and there were many times I was genuinely afraid the book would end with Medea becoming yet another statistic in her world. I definitely recommend checking it out.