I can't add much to the writeups above. However, I feel that I should chime in with additional positive review, simply because I generally don't much want to read a dark, violent, gothic, science fantasy novel. A ghost in space is not generally attractive, and a skeleton army in space is just dumb. The adjectives used in the book jacket blurbs are uninspiring -- 'pulpy', 'heart-poundingly epic', 'sharp as a broken tooth, 'goofy and gleaming' -- basically no one knows what to say about it, and most reviews just end up saying something along the lines of "lesbian necromancers in space, what's not to love?"
But despite all of that, this was a really good book.
This is a twisty mystery with many moving parts and a new set of rules that are both predictable enough to make things interesting and unpredictable enough to surprise you. It's a treasure hunt in an ancient mansion only slightly less epic and mysterious than Piranesi; the lurking evil forces are mysterious, twisted monsters worthy of The Rook; the cast is as dark and varied and contentious as The 7 1/2 Deaths of Evelyn Hardcastle. It is A Night in the Lonesome October as written by Martha Wells... or something. Anyway, while it is not going to make the ranks as one of my favorite books, I will be reading the rest of the series, and I will look forward to reading it again in a decade. Don't be put off by anything so shallow as an aversion to necromancers.