The time is 1815. The heroine is Philadelphia "Delphie" Carteret, music teacher and caretaker for her sick and periodically delusional mother. The plot begins when she goes to some long-lost relatives to hit them up for money to take care of her mom, accompanied by her madcap neighbor Jenny. The relatives own a castle with a moat, into which Jenny cunningly flings herself and pretends to be drowning so the hero, Gareth Penistone, will (reluctantly) rescue her and ensconce her and Delphie at the castle, over the objections of cousin Mordred. Once ensconced, Delphie is astounded to find that the family thinks she's an imposter, because someone named Elaine has been claiming to be the Carteret daughter for the last twenty years.
This lunatic farrago of wackiness plus semi-random Arthurian references (there is also a notorious and deceased ancestor named Lancelot, and ten peppy children who all have Arthurian names) is completely typical of Joan Aiken. So are the funny names. I do not for a second believe that she was unaware of the implications of a hero named Penistone (yes, I know it's a village in Yorkshire), especially given this line of dialogue: "I don't like these angry voices and all this talk of Bollington and Penistone!"
Though a series of ridiculous events, Delphie fake-marries Gareth Penistone; needless to say, the fake marriage turns out to be real, to everyone's dismay. The ten Arthurian kids tend to a languid poet in debtor's prison, the hero poisons a sick mouse he's supposed to be nursing back to health, Mordred lives up to his name (name a kid Mordred, and you deserve what you get), and the last chapter consists of long blocks of text in which characters madly explain who secretly married who and why the impersonation-- all of which was so convoluted that I did not even try to follow it.
Funny, fluffy, utterly absurd. If it sounds fun, you will enjoy it. Some animals are collateral damage of villainous plotting.
Only $3.99 for the ebook on Amazon: The Five-Minute Marriage
Amazon has a number of similarly priced Aiken books on Kindle. Grab 'em if you want 'em!
If any of the people who wanted this book from me would rather have it in hard copy, I'll send my copy to the first who comments for Paypaled postage.