It's her eighteenth birthday, and Lady Truthful Newington - nicknamed 'Newt' - is dreaming of her debut in London, where the streets are filled with eligible young men and magic. Coming of age, she is also to inherit the Newington Emerald, a dazzling gem of mysterious power, last worn by her late mother. When the Emerald is stolen in a magic-infused storm, Newt will do anything to recover it - even disguise herself as a man and ally with the handsome-but-insufferable Major Harnett, who professes to despise womankind and harbours secrets of his own. The two are quickly swept into a perilous adventure, filled with sinister fey and shocking reveals, in which grand balls and witty banter mix with daring escapes and deadly curses - for they discover the Emerald is at the heart of a nefarious plot that leads all the way to the Prince Regent!

As Newt and Harnett battle enemies of the realm, each realises there is more to the other than meets the eye: despite mutual disdain and mortal danger, could they actually be falling in love?

In Newt's Emerald, bestselling author Garth Nix shares his own love for the Regency romantasy genre in a charmed world where everyone has something to hide.

Tropes include:
- Regency romance
- Romantasy
- Enemies to lovers
- Disguised as a man
- Witty banter
- Nefarious plots.