Pretty good. Despite being a known story device in the vein of My Fair Lady, the writing style, plot, and characters were all interesting and vivid and engrossing enough to keep me engaged throughout.
It never did quite take off to be as good as I'd hoped, perhaps. It suffers throughout from being a little long-winded in the internal dialogue. This was most evident in the scene where the actual proposition (bet) takes place; this should be the grand setup, the thing that kicks it all off, here we go! But there's just paaages of internal speculation and dissertation that take the pace out of it all.
There's also a couple of occasions when the speech seems altogether out of place; I'm certain a Victorian-era gentleman or lady never said "Sweet!" in response to getting their way, or decreed defiantly, "That's not happening." But most of the time it's a pretty standard historical romance, and it reads just fine.
All in all, a pleasant and quick read. Not great, but certainly more than OK and a fun way to pass a beach day.