Gideon the Ninth Book Review: A Brilliant Science Fantasy Mystery

Tamsyn Muir’s debut novel, Gideon the Ninth, is an ambitious science fantasy adventure unlike almost anything else in the genre. Combining necromancers, sword fighting, ancient secrets, sarcastic humor, and a locked-room mystery, the novel delivers a reading experience that is strange, complicated, and incredibly entertaining.

At the center of the story is Gideon Nav, an orphan who has spent most of her life trapped in the gloomy and isolated Ninth House. Gideon wants nothing more than to escape, leave the Ninth House behind, and enlist in the military. Unfortunately for her, escaping is much easier said than done.

Her plans are interrupted by Harrowhark Nonagesimus, the teenage necromancer and heir to the Ninth House. Gideon and Harrow have spent years fighting, insulting, and undermining each other. They are about as far from friends as two people can be.

However, when the Emperor summons the heirs of the Nine Houses to participate in a mysterious competition, Gideon and Harrow are forced to work together. What follows is a dark, funny, and unpredictable story filled with deadly challenges, complicated relationships, and mysteries that become more dangerous with every passing chapter.

Keep reading for a short summary of the novel and why Gideon the Ninth should be your next read.

Gideon the Ninth Summary

Gideon Nav is an orphan who has been raised in the Ninth House for as long as she can remember. The Ninth House is a dark, isolated place filled with skeletons, religious traditions, and necromancers. Gideon has never felt like she belongs there, and she has spent years dreaming of leaving.

At the beginning of the novel, Gideon is preparing to escape once again. Her plan is to leave the planet and enlist in the military, where she believes she will finally have a chance to build a life of her own.

However, Gideon’s escape plan quickly falls apart when Harrowhark Nonagesimus interferes.

Harrowhark, often called Harrow, is the heir to the Ninth House and an extremely talented necromancer. She is also Gideon’s greatest rival. The two have a long and bitter history together, and neither of them has much reason to trust the other.

Harrow needs Gideon’s help because the Emperor has summoned the heirs of the Nine Houses to the ancient home of the First House. Each heir must arrive with a cavalier, a trained fighter who will protect and assist the necromancer during the trials ahead.

The Ninth House has very few options, and Gideon is one of its strongest fighters. Harrow offers Gideon a deal: serve as her cavalier, help represent the Ninth House, and Gideon may finally receive the freedom she has wanted for years.

Gideon reluctantly agrees.

When Gideon and Harrow arrive at the First House, they meet the necromancers and cavaliers representing the other Houses. Each group has its own abilities, traditions, personalities, and secrets.

The Emperor has called them together for a mysterious purpose. Those who successfully complete the trials may become Lyctors, incredibly powerful and seemingly immortal servants of the Emperor.

The problem is that nobody fully understands how to become a Lyctor.

The participants must explore the enormous, decaying building, search for clues, complete dangerous experiments, and uncover the knowledge needed to transform themselves. They are not allowed to leave until the process is complete.

Then people begin to die.

What initially appears to be a strange competition quickly turns into a deadly mystery. Gideon and Harrow must determine whether a monster is hiding inside the building or whether one of the other competitors is eliminating the opposition.

Despite their mutual dislike, the two are forced to depend on each other. The deeper Gideon investigates, the more she realizes that the competition is connected to secrets much larger than the Ninth House—or Gideon herself.

Gideon the Ninth Book Review

Reading Gideon the Ninth was one of the most unusual and entertaining experiences I have had with a fantasy novel. The book blends multiple genres without ever feeling like it is simply following a familiar formula.

It is part science fiction, part fantasy adventure, part horror story, and part murder mystery. There are spaceships and distant planets, but there are also swords, ancient tombs, magical rituals, and necromancers who can manipulate bones and dead bodies.

While the novel is usually described as science fantasy, it often feels more like a fantasy novel set inside a science fiction universe. Readers who normally prefer fantasy should not be discouraged by the futuristic setting. The story is much more focused on magic, relationships, mysteries, and survival than it is on explaining technology.

One of the strongest elements of the novel is its world-building.

Tamsyn Muir creates a universe ruled by an Emperor and divided among Nine Houses, each with its own traditions and approach to necromancy. The Ninth House is associated with tombs, darkness, bones, and religious devotion, while the other Houses have their own cultures and specialties.

Muir does not reveal everything immediately. Readers are introduced to only parts of the larger universe, especially the Ninth House and the First House. That makes the setting feel enormous, with countless histories and conflicts waiting to be explored in future books.

The world-building can occasionally be confusing because the novel introduces many characters, Houses, magical abilities, and titles in a relatively short period. It may take readers some time to remember who belongs to which House and how each character is connected to the larger competition.

However, the confusion also adds to the mystery. Gideon does not completely understand what is happening either, so readers discover the truth alongside her.

Gideon Nav Is an Unforgettable Main Character

As impressive as the world-building is, Gideon’s personality is what makes the novel truly memorable.

Gideon is sarcastic, rebellious, impulsive, and frequently inappropriate. She does not behave like a traditional fantasy hero, and she certainly does not speak like one. Her observations and jokes bring energy to scenes that could otherwise become dark or overwhelming.

Her humor also gives the novel a distinctive voice. Many fantasy books feature complicated magical systems and serious political conflicts, but few are willing to be as strange and funny as Gideon the Ninth.

Gideon’s personality helps balance the darker parts of the story. The novel includes death, violence, disturbing experiments, and unsettling discoveries, but it never becomes relentlessly bleak. Gideon always seems ready with a joke, insult, or sarcastic observation.

In that sense, the novel occasionally reminded me of The Hitchhiker’s Guide to the Galaxy. The two books are very different in terms of plot and setting, but both understand how humor can make a complicated science fiction world more accessible.

Blending science fiction and comedy is difficult. An author has to establish the world, explain unfamiliar concepts, develop the characters, and maintain the tension without allowing the jokes to undermine the story.

Muir handles that balance extremely well.

The humor does not make the danger feel less real. Instead, it makes the characters more human and gives readers a reason to become emotionally invested in them.

Gideon and Harrow’s Relationship Drives the Story

The relationship between Gideon and Harrow is another major strength of the novel.

At the beginning of the story, the two characters genuinely dislike each other. Their history is filled with resentment, cruelty, competition, and anger. Gideon sees Harrow as the person standing between her and freedom, while Harrow views Gideon as someone difficult to control.

Their partnership is based on necessity rather than friendship.

As the mystery develops, however, Gideon and Harrow are forced to trust each other. They must combine Harrow’s necromantic abilities with Gideon’s strength and sword-fighting skills if they hope to survive.

Their relationship develops gradually, which makes it much more believable. The novel does not suddenly erase years of hostility. Instead, it allows both characters to understand each other in ways they never had before.

Some of the best moments in the book come from their arguments, reluctant teamwork, and growing respect. Their complicated bond gives the story its emotional center and prevents the novel from becoming nothing more than an elaborate magical mystery.

A Fantasy Novel With a Locked-Room Mystery

The mystery element of Gideon the Ninth was another pleasant surprise.

Once the characters arrive at the First House, the novel begins to resemble a locked-room mystery. A group of competitors is trapped in an isolated location. They cannot easily leave, communication is limited, and somebody—or something—is killing them.

Everyone has secrets, and almost everyone has a possible motive.

Gideon begins investigating the deaths while also trying to understand the trials. The old building is filled with hidden rooms, strange laboratories, forbidden doors, and evidence of experiments that may have gone horribly wrong.

This gives the novel a strong sense of atmosphere. The First House feels abandoned and haunted, even when it is filled with people. The characters never know what may be hiding behind the next door or whether the person beside them can be trusted.

The mystery becomes increasingly complicated as the novel progresses. New discoveries raise more questions, and the competition turns into a desperate fight for survival.

Readers who enjoy books that blend fantasy with murder mysteries should find a lot to enjoy here.

Is Gideon the Ninth Worth Reading?

Gideon the Ninth is absolutely worth reading, especially for readers who enjoy books that refuse to fit neatly into one genre.

The novel features a complex universe, memorable characters, clever humor, magical battles, and a mystery that becomes more intense as the story progresses. It is imaginative without feeling familiar, and it takes risks that many fantasy novels avoid.

The story may be challenging at first because of the large cast and the complicated world-building. Readers are introduced to several necromancers, cavaliers, Houses, and magical concepts, and it can take time for everything to come together.

However, patience is rewarded. Once the mystery takes over, the novel becomes difficult to put down.

I finished the book in only two days because I wanted to know what was happening, who could be trusted, and how Gideon and Harrow would survive. Every new discovery made the story more intriguing.

What I loved most was the combination of an original plot, wonderful characters, necromancy, sword fighting, and humor. The jokes land, the action is exciting, and the emotional moments feel earned.

Final Thoughts

Gideon the Ninth is a refreshing and imaginative debut from Tamsyn Muir. It combines science fiction, fantasy, horror, and mystery to create a novel that feels completely unique.

Gideon is a fantastic protagonist whose personality and humor make the book stand out. Harrow is equally fascinating, and the complicated relationship between the two characters gives the story depth beyond its mysteries and magical battles.

The world of the Nine Houses is detailed enough to feel real while still leaving plenty of unanswered questions for the rest of the Locked Tomb series. That sense of mystery makes the universe feel much larger than what readers see in the first novel.

I highly recommend Gideon the Ninth to fantasy lovers, science fiction fans, mystery readers, and anyone looking for a book that is funny, dark, unpredictable, and unlike anything else on the shelf.

It is a complicated novel, but it is also an entertaining one. Come for the necromancers and sword fights, and stay for Gideon’s humor, the deadly mystery, and the unforgettable relationship at the center of the story.

Rating: 4.5 out of 5 stars

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