In this Gideon the Ninth review, I’m going to break down why Tamsyn Muir’s debut isn’t just a funny tagline—it’s a masterclass in atmosphere, voice, and character dynamics. Despite some pacing hurdles, this has easily become my favorite read of 2025 so far.
If you spend any time in sci-fi or fantasy circles, you have likely heard the pitch: “Lesbian Necromancers in Space.” It is a catchy meme, but does the book actually live up to the hype?
The Verdict at a Glance
Rating: ⭐⭐⭐⭐⭐ (5/5) Genre: Science Fantasy / Horror / Sci-fi Perfect for fans of: Warhammer 40k aesthetics, locked-room mysteries, and enemies-to-lovers arcs.
The Hook: Locked In From Chapter Two
The book opens with a disorienting cold open, but by Chapter 2, I was locked the fuck in.
Muir establishes a narrative voice for Gideon Nav that is unparalleled in modern SFF. Gideon is rude, hilarious, obsession-worthy, and tragically resigned to her life of servitude among the “ossifying nuns” and skeletons of the Ninth House. She wants out, but instead, she is dragged into a deadly trial of wits by her childhood nemesis, Harrowhark Nonagesimus.
The Setting: A Haunted Puzzle Box
The bulk of the novel takes place at Canaan House, a massive, decaying structure that initially feels like a gothic hotel.
I will admit, the pacing at the start of the Canaan House section is a slow burn—a stark contrast to the frenetic energy of the opening chapters. It requires patience. However, once you hit the halfway mark, the book sheds its skin. The realization that this is more than just a diplomatic trial—that the characters are essentially stuck in a deadly, high-stakes “escape room” filled with eldritch horrors—changes everything.
Character Dynamics: Devotion and Silence
The relationship between Gideon and Harrowhark is the beating heart of the story. This isn’t a cheap romance; it is a jagged, painful journey from enemies to reluctant partners.
Their evolution feels incredibly natural. They realize they need to work together to survive the trials. Seeing that necessity breed respect—and eventually absolute devotion—is the book’s greatest triumph.
A Note on the POV There is a section in the middle of the book where Gideon is forced into a vow of silence. For readers who love Gideon’s snark, this might feel frustrating, as she is effectively underutilized in these scenes. However, looking back, this was a strategic masterstroke by Muir.
By silencing the protagonist, the narrative lens is forced outward. It allows the cavalier and necromancer pairs of the other Houses to shine. Because the side characters are given this space to breathe, the eventual stakes feel incredibly real. When the twists start coming, they hit hard because we actually care about the supporting cast.
The Mystery: Twists That Pay Off
Without spoiling the plot, I have to credit the construction of the mystery. Gideon the Ninth plays fair with its readers. I had suspicions about certain characters early on (specifically regarding the Seventh House), and seeing how those threads unraveled was deeply satisfying.
The twists are relentless, the “deaths” are shocking, and the climax is an emotional gut-punch.
Final Thoughts
Despite a deliberate start to the central mystery, I stormed through the final act at lightning speed. Gideon the Ninth is a masterwork of tone, seamlessly blending meme-literate humor with deep, gothic horror.
If you like puzzles, swords, skeletons, and devotion that transcends death, pick this up immediately.