I'm not a huge mystery reader, but in general I've found that conclusions to these sorts of stories go one of two ways:

1. Scooby Doo reveal. The villain was a minor character who jumps into the foreground to explain how they were involved the whole time.

2. The logical villain. Under these circumstances it normally requires the author to throw in a lot more misdirection, potential candidates, and red herrings so that people who like logic puzzles don't just immediately figure it out halfway through.

I don't necessarily care about twists, so I genuinely don't mind the logical villain. What's odd about the Ninth House is it has it both ways. There's a logical suspect, and a Scooby Doo suspect who's revealed a power above and beyond the logical suspect, like the final few hours of nearly every Final Fantasy game.

The logical suspect is easy to guess because of the themes more than the evidence, because this book has a pretty strong anti-authority leaning which I generally enjoyed.

I'm almost tempted to give this book a better rating. The characters, as with most Leigh Bardugo books, are well-realized and all seem to have internal live of their own. The magic systems are well thought through and make sense.

This is a personal beef, one that comes from years of flipping over interesting looking books, getting halfway through the description, and finding out that they're always detective stories. Some truly out there mysteries get deflated halfway through when I found out it's another cop or detective, and they're often chasing a serial killer that chose them specifically. These stories almost always have an authoritarian leaning that I find off-putting.

Ninth House isn't that bad, but Alex is effectively an Ivy League magic cop. And the story definitely takes some quality potshots at the things privileged people have massive blindspots towards. But so often it just drifts back into those detective tropes and I don't think that necessarily serves the character well. The strongest moments often come from Alex defying her role.

A friend of mine, in fact the person who keeps recommending Bardugo books, once joked that a heist is just an inside-out mystery, which would explain Bardugo going from one to the other. But I think my preference for heists over mysteries is that heists often involve people trying to defeat or undermine power, whereas a lot of mysteries can often simply reinforce power (I don't need examples to the contrary, I know they exist, it's a big genre).

Ninth House was an entertaining enough read, but seems awfully conventional compared to her fantasy books.