Just another GR refugee. Other than that, I had a stroke in 2004, and read almost anything I can get my hands on, though I have a particular weakness for history, mystery, and historical fiction.
Cotillion, appropriately enough, is a novel about four couples. (The Cotillion is a period dance, with four couples, and was one of the ancestors of the American "square dance.")
Kitty Charing is in a pickle. Her adoptive father, generally known as "Uncle Matthew," a penny-pinching miser of an old grouch, has decided that he shall leave his fortune to her - if she marries one of his great-nephews. (I tell you, there really should have been a square for "Cousin Marriage" in the Romance Bingo.) Otherwise, she will be left penniless, and he will leave his money to charity.
So he invites all five of these nephews down for the weekend, so Kitty can make up her mind. Four men attend: her slow-witted cousin Dolph (he is, however, an earl - but "only" an Irish one, and very much under his domineering mother's thumb), another who is a prim and prissy vicar, the vicar's older (and married) brother, George, and Freddy Stanton - a "Pink of the Ton" (read: fashionista) who neither needs Matthew's money, or wants to get married. The two not attending are the one in the army, and Jack, Matthew's (and Kitty's) favorite, who is more than a bit of a rascal.
Dolph and the vicar promptly propose, and Kitty declines them. She then proposes to Freddy - a fake engagement, and a very real trip to London. (She has always dreamed of going to London, and her other plan is to make Jack jealous. So that he will propose to her, of course.)
Down in London, she drags Freddy through almost every tourist trap in town, and leads all of the folks she meets, from Freddy's scatter-witted sister to her only living relative, Camille, on a very merry dance. Luckily for all involved, Kitty has a good heart, and Freddy a lot of common sense.
Since this is one of Heyer's regency romances, there are happy endings all round, of course.