The lady most likely - Julia Quinn

Hugh Dunne, the Earl of Briarly, needs a wife - so his sister hands him a list of the very best young ladies on the market. And then, because he refuses to tear himself away from the stables where he trains Arabian racehorses, she invites all those ladies to a house party, along with some other bachelors, of course.

So who will Hugh choose? The Botticelli-esque, enchanting Gwendolyn? The outspoken, delightful Katherine? If he doesn't work fast, he'll lose those ladies to his closest friends, and then where will he look for a wife? Perhaps, just perhaps, toward a lady who's not on a market at all, and would require a great deal of persuading . . .