Nona the Ninth is Tamsyn Muir's boldest gambit yet, completely upending reader expectations by trading the gothic space necromancy of previous Locked Tomb books for what initially feels like slice-of-life urban fantasy. Following Nona, a mysterious girl with no memory living in a war-torn city with her makeshift family, the book spends its first half focused on school days, household dynamics, and small domestic moments.

This dramatic tonal shift will frustrate readers expecting immediate answers about Harrow and Gideon's fates, but Muir's characterization of Nona—childlike yet ancient, loving yet dangerous—anchors the narrative beautifully. The supporting cast, particularly Nona's protective guardians Camilla and Palamedes (now sharing one body), crackles with lived-in authenticity.

Muir excels at writing found family dynamics, making readers genuinely care about these characters' mundane struggles before the cosmic horror crashes back in. When the book's true nature reveals itself in the final act, the emotional devastation hits harder because of this careful groundwork.

The climax delivers spectacular action and long-awaited revelations about the series' central mysteries, though some plot threads feel rushed after the deliberate pacing of earlier sections. Muir's prose remains sharp and funny, though her tendency toward oblique storytelling reaches new heights here—casual readers may find themselves lost without detailed knowledge of previous books.

The violence, when it comes, is visceral and disturbing, particularly scenes involving Nona's true nature. This is essential reading for Locked Tomb devotees who trust Muir's vision, but newcomers should absolutely start with Gideon the Ninth. Readers seeking straightforward fantasy or quick plot advancement should skip this entirely. However, those who appreciate experimental narrative structure, complex character work, and stories that subvert genre expectations will find Nona rewarding, even if it's the series' most challenging entry. The book succeeds as both intimate character study and explosive space opera finale, proving Muir's range while advancing her overarching story in unexpected directions.