This is a reluctant two-star review. I think the bones and underlying worldbuilding of Brimstone are worth four stars, but the execution itself failed in convincing us, the readers, to experience that worldbuilding.
What I mean by this is that it seemed as though the author spent a great deal of time thinking about their story, their characters, and the world it all exists in... but then forgot to let us in on the secret. Character relationships lack context, the story flips from one scene to the next without much reason for investment, and it just generally feels as though most of the book takes place in the author's mind instead of on the page.
Many books face the problem of being long-winded; they take far too long to get to the point, and you end up with a story that could do with 20,000 fewer words. Brimstone is the opposite. Many revelations and connections are hidden away from us. This story could use 20,000 more words, if only to build upon the relationships and ambitions we're expected to care about. It is a novella, so this mostly makes sense. A trilogy can't and shouldn't be contained to a novella; otherwise, why is it a trilogy?
The main character, as well, seems poorly portrayed. A strong, observant female lead is good, but how she's portrayed to us leaves a bit to be desired. To be specific, Ava seems more a caricature than an individual. The same responses recycle throughout the story, and it is unclear why she behaves the way she does. We're treated to a sad origin story, but not to the connections between that story and how she acts in the present. Everything is about sex, and almost every scene makes sure to mention how something smells or tastes. This structure is repeated, again and again, to the point that I once considered that Ava was flicking her tongue out like a snake to taste the air because that would be the only way it made sense. As well, her penchant for sex usually borders on the inappropriate or the unreasonable; her job is, of course, focused on sex, but it was a little odd that Ava's first instinct when meeting a wraith who had just escaped violent slavery and whose people were known to be off-limits for all was to immediately have a night of passionate sex, loudly enough that all the neighbours overhear.
(Ava aside, it's a little uncomfortable for the wraith himself. He's at her mercy, essentially, and the price for his safety is having sex with a strange woman. I feel like if the genders were reversed, this scenario would be received very, very differently.)
Don't get me wrong, Ava is not a bad character. As mentioned, the bones of Brimstone are good, better than average. All of my worries and complaints would be resolved with better editing and more substance. Ava's behaviour in particular would make more sense with more context, and repetition is a problem solved by variety. The snake comparison was smarmy, but in all actuality, it'd be fine if there was some established reason for why she was so focused on tastes and smells, and if it simply weren't mentioned quite so much.
I mentioned editing, and I'll talk about that for a paragraph here. The editing, largely, is fine, but there are some clear instances where machine-assisted tools were used and the suggestions were simply accepted. These tools are notorious for replacing the right word with the wrong one, and that happens a few times while you're reading. Our minds are good at glossing over these mistakes, but in Brimstone they were unfortunately quite obvious. There were also a few missing words, again, in places where the mind doesn't simply ignore them. This is not a big deal (not even worth docking a point for), but I mention it because I think it might be connected to the overarching problem of there not being enough context for readers to properly enjoy the story. Put differently: It feels like the author rushed completion of the story. They thought about it so much that they wanted it done, but this was to our detriment. More content and more refining would have done Brimstone very well. Letting a machine do a round of editing and accepting what it says sight unseen feels, to me, like a proclamation of "I just want this done and over with," and within the context of much information being secret to the reader and instead locked away in the author's mind somewhere... well, that makes sense. Maybe that isn't what happened, but it seems to parse for me.
This is a "good" two-star rating, largely because the problems have nothing to do with substance. I'll read the next book because the worldbuilding is well done. The writing itself is good quality. I just really hope that we're let in on all the things that make the worldbuilding worth it. Why do these characters matter? Why do they act the way they do? Why does the story matter? What motivations do these characters have? The next story being novel length will help a lot, I think.
I realize two stars is discouraging ("it was okay"), but to other readers: If you like fantasy, this is worth checking out. The problems with the book are execution-based, and will almost surely be improved upon in the second book. And since this first one is a novella, it's a very quick read. I think it's a situation where there will be a payoff if you stick with it.