"Gideon the Ninth" is a science fiction novel by Tamsyn Muir that combines elements of necromancy and space opera. The story follows Gideon Nav, a rebellious young woman who is forced to serve the necromancer Harrowhark Nonagesimus in a deadly competition to become a powerful servant of the Emperor. Set in a universe where the dead can be raised and manipulated, the novel explores themes of loyalty, identity, and the complexities of relationships. As Gideon and Harrow navigate treacherous challenges, they uncover dark secrets that could change their lives and the fate of their world.