Review contains spoilers. Content warnings for trauma, torture, suicide attempts, brief discussion of sex. There's a lot more in the book that I don't mention here.
While this was not quite as bad as I expected it to be, even if you ignore the fan fiction angle, this is book is still pretty bad.
There is absolutely no reason for it to be 1000 pages, most of it is the same miserable things over and over. The characters are less than one-note, they have very little personality, and Hermione- I mean, Helena, is either the most passive martyed-to-her-fate doll, which is about 95% of the time, and the rest she goes full kamikaze warrior or tries to kill herself: The woman has no middle gears.
The first 30% of the book is a conga line of misery and abuse, it does improve slightly when Helena gets her memory back, and we get the main meat of the book in a huge flashback. However, this is where the repetition really starts to become a problem: It's just Helena exhausting herself for people who don't appreciate her, going to collect herbs, meeting Drako/Ferron, and them both slowly trapping each other in a mutually toxic relationship (the book does not shy away from calling it what it is, I will give it that much credit).
I also give the book credit for the more realistic portrayal of PTSD, especially at the very end of the book where they try to live safe and quiet lives. However, again, this is the only realistic aspect, the amount of trauma (and brain damage) Helena goes through feels like torture porn in places. Even with the book's focus on alchemy and magical healing, it really stretches the imagination that she's able to survive the injuries that she does (she does not come out of the book physically unscathed though). It's a little less gratuitous with the damage done to Ferron, as he is undead for the majority of the book, but it still feels less like hurt/comfort, and more like torture porn.
The sex scenes feel perfunctory, empty, and non-descriptive, they are not graphic at all, unlike the scenes of injury and torture. But there was one scene that I did appreciate, where Helena is trying to reclaim her sexuality and love after getting her memory back, but is overcome by her PTSD.
The world building is interesting at first glance, but feels like it's cobbled together from other sources which did it better: I found myself thinking of Planescape and Full Metal Alchemist, and, obviously Harry Potter.
I cannot recommend this book unless you are terminally curious, I read it out of sheer train wreck curiosity.