“Gideon the Ninth” is the first book in the “Locked Tomb” series by Tamsyn Muir. Set in a dark and decaying universe, the story follows Gideon Nav, a skilled swordswoman and irreverent protagonist. She is reluctantly dragged into a deadly competition where necromancers from different houses must join forces with their cavaliers to solve a mysterious puzzle. Gideon finds herself paired with the enigmatic and formidable Harrowhark Nonagesimus, a necromancer of the Ninth House, with whom she shares a tumultuous and complex relationship. As they navigate a treacherous haunted palace filled with dark secrets, sinister magic, and political intrigue, Gideon must uncover the truth behind the puzzle while confronting her own past. This gripping blend of science fiction, fantasy, and macabre elements offers an intriguing tale of necromancy, loyalty, and self-discovery in a world teetering on the brink of destruction.