best (and worst) Jane Austen sequels?

I've seen a ton of books that advertise themselves as sequels or prequels to Jane Austen's works - Days and Nights at Pemberley, Darcy's Story, etc. Which are worth reading and which aren't?

I've tried three or four and been unable to get more than half way thru any of them. So one would have to come very highly recommended for me to be even slightly tempted.

I enjoyed Joan Aiken's Jane Fairfax and Mansfield Revisited. Critical opinion of her Austen interventions is divided, but they're fun to romp through, anyway.

Emma Tennant managed two sequels to Pride and Prejudice - Pemberley & An Unequal Marriage; one to Sense and Sensibility - Elinor and Marianne; and one to Emma - Emma In Love.

Allied to these works she has also produced works relating Dr Jekyll and Mr Hyde, Jane Eyre, Tess}, and a novel about Ted Hughes and Sylvia Plath.

This does make her sound a little like a hack but surprisingly she actually a good writer, probably under-valued at present.