The Duke’s transformation was absolute, down to the very marrow of his bones. There wasn’t a single hint of self-consciousness about him. His demeanour, the set of his mouth, the lazy sway of his hand, all belonged to Lady Rose. The ease with which he changed his skin was frightening. [loc 812]
Untamed is set in something like the Regency period (see below for qualifiers); it is a romance; the Duke does dress up, gloriously and in the outmoded style of the previous generation, as 'Lady Rose'. He does leave London to stay with Katharine ('Kit') Sutherland -- sister of one of his many, many conquests -- and is horrified to discover that she works hard, morning to night, to keep the household fed and the money coming in.
None of that is especially useful either.
I think I must have heard about Untamed when it first came out: apparently I bought it four years ago, though have only just got around to reading it. And rereading. It is a glorious novel, suffocatingly intense and sensuous in the broadest usage of the term. Kit and the Duke are utterly fascinating, as is the changing detente between them. At times I was reminded of Dunnett's heroes, vulnerable and vicious and too clever for their own good: at times of Heyer's tougher and more practical heroines (and heroes, for that matter). And while on first reading I was rudely flung out of the novel by a scene that I simply could not believe in (the ball, with Kit's grand entry: I stopped reading at that point and set the book aside for a couple of days) I couldn't stay away.
So my approach to some of the more anachronistic, less credible moments -- there are a few, though nothing on the level of that particular scene -- is to treat the novel as an alternate history, possibly even a fantasy (sans magic). There are certainly aspects that jar horribly with the conventional Regency setting, and turns of phrase, or thought, that sound disconcertingly modern: but those potential flaws make perfect sense for the characters. (And yes, there are Corn Laws, and a potential rival for the Duke's title, and glancing mentions of a more familiar nineteenth century: but these are background.)
The secondary characters in Untamed are well-drawn -- especially brother Tom with his secret hobby -- but nobody feels quite as real as Kit. I find her pragmatic approach to life thoroughly satisfactory, and the perfect foil to the beguiling Duke.
I like Anna Cowan's prose: simple, evocative phrasing -- 'his heart alight with hopeful anticipation' -- blended with rawly specific descriptions of emotion and its outward effects. I'd like to see what she does next.