I stumbled across this young adult gem as a read-alike to Georgette Heyer and Jane Austen. A smart, exciting mix of Regency and fantasy, "Newt" refers to Lady Truthful Newington and her "emerald" is a magical heirloom stolen during a family party on her eighteenth birthday. The precious stone's properties are properly harnessed only by the owning family which puts the Newington's in peril of misfortune and possibly worse if the jewel gets into the wrong hands. Lady Truthful's bumbling cousins want to help, but it's clear they make every situation more difficult with their rough housing and immaturity. So Truthful sets off alone on a quest not quite befitting a lady in order to retrieve the emerald herself.
Lady Truthful travels to London and disguises herself as a man in order to learn more about the whereabouts of the missing emerald and who might be behind its theft. In doing so, she joins forces with a dashing military Captain who initially mistakes her for a spy. The two battle pirates, a wicked witch, conjured storms, charms, and enchantments. It turns out that the bumbling cousins prepared Truthful very well for a life of high adventure and she holds her own during each escapade.
In between kidnappings, swashbuckling and horse chases, Lady Truthful must fulfill her duties as an eligible young lady out for "the season." She's also developed a bit of a crush on the military Captain. After a number of balls, a trip to Brighton, and a masquerade, all's well that ends well. Short, sweet, packed full of honor, valor, and all the manners, rules and regulations required of a young lady, this novel combines the best of Regency era tropes with the fantasy Nix is known for in his Abhorsen or Old Kingdom series featuring the character Sabriel.