Garth Nix's fantasy is full of stuff that isn't exactly typical -- schoolgirl necromancers, color-coded castles and an asthmatic boy made into the heir of the universe. 
 So it's a little surprising that "Newt's Emerald" settles comfortably into the niche of Regency fantasy, with all the dances and misunderstandings both magical and romantic. But fear not -- this clever little novel is full of mystery elements, action-packed escapes, magical disasters and the odd bout of enchanted cross-dressing, and Nix balances out the romance, Regency trappings and action like a skilled juggler. 
 On her eighteenth birthday, Lady Truthful Newton ("Newt" to her three male cousins) is given a rare and valuable heirloom: the Newton Emerald, a strange magical jewel. But mere seconds later, lightning strikes nearby, the room goes dark, and the table is overturned... and Truthful realizes that the Emerald has been stolen. Her devastated father takes to his bed, and her cousins all immediately vow to go on globe-trotting adventures to find her a new sorcerous emerald. 
 With nothing more she can do, Truthful goes to London for her "coming-out," under the wing of the eccentric Lady Badgery. And her great-aunt wastes no time in sending Truthful to investigate the Emerald's theft -- though of course, for the sake of her reputation, she has to disguise herself as a male French cousin. 
 As she investigates, she finds herself working with the brusque Major Hartnett, who has already taken a strong dislike to Lady Truthful (but doesn't mind her "French cousin" much). And after someone close to Truthful goes missing, she learns of the sinister person who has been scheming for years to get the Emerald -- and the terrible possible uses of the jewel, some of which could threaten the safety of all England. 
 The sign of a truly great writer is that they can take a simple story or a much-explored genre of story, and bring something new, brilliant and captivating to the same old tropes. "Newt's Emerald" is a pretty prime example of that occurrence -- at first it feels a bit like the Regency fantasies that have popped up since "Jonathan Strange and Mr. Norrell," with the young lady finding her way in a London of balls, sorcery, glamours and social conflict. 
 But this Regency story is more about the spy-thriller antics than the lacy dresses and balls. Nix weaves in some thrilling captures and escapes (including Truthful's desperate escape aboard a French ship), malignant spells, international espionage and magical mustaches, with Truthful floating in the middle with no idea how to deal with all this mayhem. 
 And Nix resculpts his distinctive writing style into something more appropriate for the tale. His writing here is a little more formal and distant from Truthful and the other characters, but still graced with some funny moments ("Besides, if I hadn't dressed as a man and been captured with you, then you'd be drowned by now!") and glimmeringly beautiful descriptions, though sparer and less common than Nix's later work. This was a story written early in his career, which took some rewriting and time to coalesce into its present form. 
 The problem? That would be the hints that the Emerald is going to be used by Napoleonic loyalists, but this particular plot thread just sort of putters out and fades away. It felt like it could have been used more effectively. Of course, there's still a romance -- a bit of a "Pride and Prejudice" affair, with clashing mistaken identities -- but it's woven smoothly into the rest of the tale, so the growing love feels relatively organic. 
 Truthful is a well-written heroine whose behavior usually makes sense -- she's smart, strong and capable, but also sheltered about the world of London sorcery and political conspiracy. Nix never lets her seem too modern or knowledgeable, and it makes her even more likable. On the flipside, we have Harnett, who is clearly not what he seems to be from the beginning. He's a bit too much like Truthful in all the right and wrong ways, being blunt and quick to take offense (he initially dislikes her because she inadvertently snubbed a guy he knew), but he slowly learns to appreciate her courage and ingenuity as the story winds on. 
 "Newt's Emerald" is an enchanting read for those who appreciate Regency fantasy -- especially the kind that involves war and espionage rather than just fans and dancing. Clever, brisk and full of likable characters, chases and the occasional magical mustache.