This might be the best use of title I've seen in a book yet. There's something uniquely ominous about starting a book entitled The Death of Jane Lawrence only to find from the very first page that the protagonist is a Jane who is not a Lawrence yet, but is actively trying to marry into that name. It also makes for a very interesting counterbalance to the natural wanting-things-to-go-well-for-the-protagonist that comes with an absorbing story with a relateable lead. I forgot the title pretty quickly in my absorption, and the farther I read, the more sobering the title was and the less I wanted to take it at face value.
This is a horror book! It's all very Gothic-esque: the house itself taking up as much weight as a character on its own, relationships as a source of both terror and desire (alternately, mostly), spooky atmosphere, vague-but-extremely-threatening danger both physical and psychological, and so on. Interestingly, the things which caused the most fear in Jane - though understandable, especially given various things which made her mind not work as rationally as usual (lack of sleep, for one) - were not the things that really stuck with me. Not sure if this is the way horror usually works, or if it's just my personal way of engaging with it, but what I find most horrifying overall is that which is most understated. Those little things that niggle away at you after you've put the book away, even after a satisfying conclusion.
Which is to say: this book had that. It had both! Upfront horror, understated horror, the works!
Also it was very absorbing; had a resonance in its magic system - though I hesitate to call it a "system" as such; had a lead who, despite a plot which had her mostly reacting to her environment, felt like a full person with interests of her own; had a woman acting desperately in defence of a man; and had a conclusion which was at once narratively satisfying and disquieting, in that niggling little way. I liked it at the start, and grew into loving it as it went.
Selling points: spooky; eldritch calculus (which is just regular calculus, but presented as EXTREMELY ELDRITCH); autistic protagonist (with a surprisingly relatable doesn't-know-how-to-deal-with-these-feelings romance); all those things in the paragraph above, really.
Warnings: gore; body horror; gaslighting (in addition to the actual gas lighting); cocaine; self-harm, ritualised; unreality; medical implements/procedures (Victorian-era); all the emotions all over the place; death; illness; confinement; problems arising from lack of clear and honest communication.