Gideon the Ninth is an ambitious genre-blending experiment that will either captivate or completely alienate readers—there's little middle ground. Tamsyn Muir throws together lesbian necromancers, locked-room mysteries, and internet-age snark in a crumbling gothic mansion floating in space, creating something genuinely unique in speculative fiction.

The book follows Gideon Nav, a sword-wielding cavalier with a mouth like a sailor and pop culture references that feel distinctly 21st century, as she reluctantly serves her nemesis-turned-partner Harrowhark in a deadly trial to become immortal servants of an undead Emperor. What starts as enemies-to-lovers banter evolves into genuine emotional complexity as the stakes escalate and bodies pile up.

Muir excels at world-building that feels both ancient and futuristic—her necromantic Houses have millennia of history, yet characters drop phrases like 'that's absolutely buck wild' without explanation. This tonal whiplash is intentional but jarring. The magic system is intricate and fascinating, grounded in bone manipulation and thanergy that feels genuinely alien. When the book focuses on the central mystery of who's murdering contestants, it's genuinely gripping.

However, Muir demands patience. The first third moves slowly as she establishes an enormous cast of characters from nine different Houses, many of whom blur together initially. The prose is dense with neologisms and assumes readers will keep up with complex political relationships without much hand-holding. Gideon's modern vernacular ('How's that for a hot girl summer, you absolute nightmare') will either feel refreshingly irreverent or completely immersion-breaking.

This book rewards readers who enjoy puzzle-box narratives, aren't fazed by graphic violence, and appreciate queer relationships that develop organically rather than being telegraphed. Fantasy readers seeking traditional epic quests should look elsewhere, as should anyone wanting straightforward prose or conventional pacing. Science fiction fans comfortable with New Weird elements will find more to love than those preferring hard SF.

Gideon the Ninth succeeds as a bold creative statement that establishes Muir as a distinctive voice, even when her ambitions occasionally exceed her execution. It's the rare book that feels genuinely unprecedented—whether that's thrilling or exhausting depends entirely on your tolerance for beautiful, chaotic experimentation.