Have had an incredibly difficult time trying to figure out how to rate and review this book. There were some elements I positively devoured: the unapologetic dark atmosphere and themes grabbed me right from the start and kept me hooked (I honestly can't believe this author debuted with a cozy fantasy and then jumped to this), the epigraphs for each chapter were so enriching, and the often unreliable characters had me foaming at the mouth as I watched madness grip them. So many parts of this book felt like a celebration of everything that writing can be, from exploring form with poems sprawled across a page (don't go the audiobook route with this one!) to every moment of shock and doom I got to feel as a reader.

That said... I'm left unsatisfied. So much was given potential and then let down by execution; a bold attempt with a last minute flinch. Not only am I unsure whether this book is a standalone or part of a series, the author seems confused too. The first few parts got so much room to breathe that I was sure this would require a whole series, only for the last 20% to try to chew and resolve everything bitten off, but choke with a chaser of deus ex machina instead. Profound moral questions around "goodness" that seemed the lifeblood of the story were layered with academia and kink to set up an absolutely fascinating exploration that went ... nowhere, with an unfortunate sense of finality. I never felt I truly understood the MC or believed why she felt as she did, despite adoring secondary characters. The core romantic relationship was incredibly contrived, and while I can see groundwork for how that may be intentional to support a sequel, I can't give credit for something that I don't know exists, and within the bounds of this book it just didn't work.

Final note: I read Shields' debut The Honey Witch nearly 100 books ago, and at that point I gave it 5 stars. Though I'm rating An Arcane Study of Stars lower, in many way I actually liked it better, and it's just that I'm reading it as a more experienced (and therefore critical) reader. I actually do feel this book is a step in the right direction for Shields, so I just wanted to explain the rating difference. I'm still hopeful for a sequel and very interested in seeing Shields develop more as an author, because I really believe she's got incredible concepts that just need pushing out a little farther.