Here is an AWESOME list compiled by Austenesque Reviews.
Check out her site for more book re-telling lists of the other Jane Austen novels.
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Epistolary
A Visit to Highbury
(originally published as Mrs. Goddard Mistress of a School in 1993)
by Joan Austen-Leigh © 1995
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Mature Audience
James Fairfax
by Jane Austen and Adam Campan © 2009
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Modern Adaptation
The Importance of Being Emma
by Juliet Archer © 2008
Amanda
Book Five in the Austen Series
by Debra White Smith © 2006
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Retellings/Point-of-view
George Knightley, Esquire: Charity Envieth Not (Volume 1)
by Barbara Cornthwaite © 2009
Lovers' Perjuries: Or, The Clandestine Courtship of Jane Fairfax and Frank Churchill
by Joan Ellen Delman © 2007
Mr. Knightley's Diary
by Amanda Grange © 2007
Jane Fairfax
by Joan Aiken © 1990
(republished in 1997)
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Sequel
Anna Weston
by Brenda Finn © 2000
Emma in Love
by Emma Tennant © 1997
Later Days at Highbury
by Joan Austen-Leigh © 1996
(epistolary)
Truth and Rumor
by Jane Gillespie © 1995
Aunt Celia
by Jane Gillespie © 1993
Jane Fairfax
by Naomi Royde Smith © 1940
(prequel)
The Journal of Jane Fairfax
by Charlotte Grey © 1983
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Short Story
Donwell Abbey by Katharine Moore © 2008
available online
Emma and Knightley
originally published as Perfect Happiness in 1996
by Rachel Billington © 2008
The Complete Mrs. Elton
The Courtship of Mrs. Elton
In Defense of Mrs. Elton
Mrs. Elton in America
by Diana Birchall © 2004
Poor Emma
a short story found in There Are No Ghosts in the Soviet Union
by Reginald Hill © 1988
(mystery)
*Thanks to Austenesqe Reviews for compiling this list!
* part of Mr Knightley's Picnic