I know there have been the fan fiction pieces that are basically sequels of the original. But these two (as well as Austenland, which I read earlier this year) take modern girls and somehow throw them into the P&P world. (Side note: There's also Pride and Prejudice and Zombies which has been incredibly popular at the bookstore.)
Prada doesn't actually relate to the P&P storyline. It's about a fifteen year old American girl visiting London for a summer trip when she falls (in Prada shoes) and wakes up in Regency times, the times of P&P. And then, for good measure, the male lead is a match for Darcy's demeanor. The other two have main characters that take Jane Austen trips to England.
The point? While the stories are cute concepts, the writing is no where near is good as the original. The authors make use of bad techniques, such as having a main character describe her appearance while looking at a mirror. So over done and it's a cop out. The characters are so typical: is every Jane Austen fan a single girl who claims to be so over love and relationships, but as soon as a Darcy-ish guy comes along, she falls hard? And I know with chick lit it's easy to pick out who the heroine is going to end up with, but come on, at least give the reader a couple options instead of just the one obvious guy.
I also started wondering if a book has ever been written that is very similar to P&P, but set in modern day and in high school. You know, a la The Taming of the Shrew and 10 Things I Hate About You? For example, with Bingley and Darcy being newcomers in town; that wouldn't work in a regular town today so much, but new students in a high school? There would totally be a riot amongst the girls. Hmm... :)