Harrow the Ninth by Tamsyn Muir

Harrow the Ninth, the sequel to the sensational best-selling novel Gideon the Ninth, turns a galaxy inside out as one necromancer struggles to survive the wreckage of herself aboard the Emperor's haunted space station.
 
She answered the Emperor's call. She arrived with her arts, her wits, and her only friend. In victory, her world has turned to ash. After rocking the cosmos with her deathly debut, Tamsyn Muir continues the story of the penumbral Ninth House in Harrow the Ninth, a mind-twisting puzzle box of mystery, murder, magic, and mayhem.
 
Part of the THE LOCKED TOMB SERIES
1: Gideon the Ninth 
2: Harrow the Ninth
3. Nona the Ninth
4: Alecto the Ninth
 
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“To read Harrow the Ninth is to enter a labyrinth haunted by loss and sacrifice and a truly top-tier selection of memes. But don't bother with breadcrumbs or red threads—you won't ever want to leave.” - Alix E. Harrow
 
“Harrow the Ninth is a psychological rollercoaster covering forty billion light-years. It’s wonderful to see the universe of Gideon expand, while staying as twisted and full of bones as ever.” - Django Wexler
 
“Maddeningly brilliant.” - Kiersten White