The novel revolves around the Hamilton family, who spend their Christmas holiday at their beach house, Carnival's Hide, where they encounter three mysterious brothers—Ovid, Hadfield, and Felix. As the story unfolds, the protagonist, 17-year-old Harry Hamilton, becomes entangled in a web of supernatural events and family secrets. The brothers' presence forces Harry and her family to confront hidden truths and personal fears, leading to a transformative experience that blurs the lines between reality and imagination. The narrative explores themes of identity, the power of storytelling, and the complexities of human relationships.

In a universe where necromancers hold power, Gideon, a skilled swordswoman, is reluctantly paired with her childhood rival, Harrow, to compete in a deadly trial that could grant them immortality. As they venture into an ancient, decaying mansion filled with secrets and puzzles, they must unravel the mysteries of their world and face sinister forces lurking within. With a blend of dark humor, complex characters, and a gripping plot, "Gideon The Ninth" is a thrilling and unique blend of science fiction and fantasy.

In this darkly imaginative and complex sequel, the protagonist, a necromancer with unmatched powers, confronts the aftermath of an epic space battle and the loss of her mentor. Now, she must navigate the treacherous politics of an immortal empire as its empress's right hand. While grappling with unreliable memories and a mind that seems to be unraveling, she faces internal and external threats, including potential madness and a lingering, enigmatic enemy. As she trains in the arcane arts of the dead, she must solve the mysteries of her past and the riddles of her present to protect the future of her world.