Delightful. As with her short stories, Cho has a rare and unerring ability to do charming without tripping over into twee, and witty without falling into smug.
You get the general idea. Comedy of manners layered with a very post-modern take on notions of power and belonging. Cho is a gloriously deft writer: as with all pastiches of styles gone-by there's a tricky balance between making the style recognizable enough for the mimicry to work while avoiding the traits which are the very reasons no one writes like that anymore, and she navigates this boundary with ease. In less assured hands the more, let's say, policital aspects (race, gender, slavery, colonialism) could have jarred horribly with the romantic elements, but they mesh beautifully; while they are quite obviously one of the main points of the novel, you never feel like they're the only one. There's nothing inherently wrong with books like that, of course, but they often lead to a sidelining of character, and Cho's obvious love of the two leads here (as well as the supporting cast) shines through the page and is irresistibly infectious.
I keep talking about balance, and walking along lines, because there are so many things here that could have gone horribly wrong but didn't. Prunella, for example. She has very strong elements of two character tropes I absolutely loathe: the Manic Pixie Dream Girl, and the Kim Bauer (persistent stupidity/stubbornness for the sole sake of plot advancement). She is ultimately neither of these things, I should stress (because AGENCY, thank fuck for agency), and it's always possible that my hypersensitivity to these tropes means they loom larger than they should, but there were several points where I rolled my eyes only to have to reassess mere pages later. She turns up unexpectedly at a ball to the man's obvious consternation; what embarrassing faux pas will she perpetrate which helps to bring him out of his shell and throw off the straitjacket of social convention? Well, she's going to do nothing at all, it transpires. Prunella exists as the heroine of her own story, not merely to support Zacharias, despite the blatant will they/will they nature of their relationship. If his competence is more reported than shown, her moments of kicking ass and taking names are a glory to behold.
My only real quibble is that the pacing is a little uneven. The first half of the book is perhaps a touch too leisurely, and while the pace picks up very nicely after the halfway mark the climax feels slightly rushed and the dénouement overly full. Still, in a debut novel, never mind one with as many other things to recommend it, this is all eminently forgivable. Sorcerer to the Crown is intelligent, wonderfully stylish, and above all fun. One book you absolutely should judge by its cover.