Gideon the Ninth by Tamsyn Muir
So I loved Gideon the Ninth. She sucked me right in with her attitude, her snarkiness, her sword. She's a fabulous character. She will tell the world she doesn't care, but at the same time is fiercely loyal and honestly cares about the other on this adventure. She is Cavalier to Harrowhark, Reverend Daughter of the Ninth House, ruler of their home planet. Harrowhark and the necromancer heirs of the other houses have all been brought Canaan House with possibility of becoming Lyctors, powerful, nearly immortal generals in the Emperor/God's army.
Gideon the Ninth is maybe sci-fi. It takes place in space, there were a couple of space shuttles, but it is much more fantasy/horror. All the combat is hand to hand or with swords. Gideon and Harrowhark, her master/crush/frenemy, are exploring what basically a gothic space castle with skeleton servants and words written in blood that appear on the walls. Or maybe it's a murder mystery. The Emperor has...