The Accidental Duchess by Jessica Benson

Skeptic scale: ♥♥♥♥♥
It was like Elizabeth Bennet's voice in my head, reading this to me in 2013, both of us giggling and in virginal white smocking nighties. Her wit and intelligence honed even further over the centuries to the fiendish sharpness of Jessica Rabbit's stiletto.

The book begins with this sly observation: 

"I married the wrong man. And by this I do not mean, as people so often do, any of the more cryptic things that you might imagine: That I awoke one morning to the realization that my husband and I had grown apart. That I discovered something about my spouse that caused me to doubt that we were well-suited. Nor, even, that I had met by chance an old love in Bond Street...What I do mean is that yesterday I stood up in St. George's, Hanover Square, and before some three hundred witnesses promised to love, honor, and obey the wrong man." 

And delightful merriment ensues.

He: A paragon, gentleman nonpareil, the illustrious Earl of Cambourne. He is also the twin of the man to whom our heroine is betrothed. His twin, younger by 15 minutes, is the frivolous and irresponsible Bertie Milburn.

She: A clever, well-born woman who has been promised to the H's brother almost since the day she was born. She comes from a political, well-connected family that contains some rather hilarious characters - including a domineering mother and be-turbanned aunt who is actually her mother's best friend (and maybe a little more?).

Conflict: A case of mistaken identity puts the h at the altar with the Earl of Cambourne, and not her intended betrothed, his brother Milburn. We learn through a series of amusing and whimsical plot twists that there's a reason that the h ends up marrying Cambourne, and it's not just all a big mistake.

The whole book was a rollicking, incredibly witty ride - a very different book than the traditional Regency romances I normally love. It was like an Oscar Wilde play - a wide, hilarious cast of characters, a loopy plot that causes people to behave in extraordinary and silly ways and just an amazing combination of cunning humor and situational comedy. Happily, JB still manages to retain the romantic (ok fine, crazysexycute) bits so it wasn't all just silliness and fun.