I posed this question on a group I belong to, but got no response, so I thought I'd post it here in hopes of getting one.
There are many novels featuring characters who first appeared in classic novels. Jane Austen's works, particularly Pride and Prejudice, seem to have spawned the most progeny. John Updike tried his hand at this in Gertrude and Claudius, which ends immediately before the action of Hamlet begins, and Sidney Carton in A Tale of Two Cities has his own book, A Far Better Rest, by Susanne Alleyn. I've enjoyed the Updike and Alleyn books, and I've also enjoyed some of Joan Aiken's Jane Austen sequels. In fact, I've tried my own hand at this with Romeo and Juliet. (My short novel, which I'm shopping around, concerns Mercutio's life before his fatal duel with Tybalt. Inquiries are welcome--just don't overload my in box, please.)
So are these novels historical novels or fan fiction? They seem to meet the criteria for fan fiction, as stated in Wikipedia: "written by people who enjoy a film, novel, television show or other media work, using the characters and situations developed in it and developing new plots in which to use these characters." Yet somehow I can't picture John Updike saying to himself, "Well, I guess I'll check Amazon to see how my Shakespeare fan fiction is selling today." Is the difference just in the quality of writing? Or is it just having a publisher's ISBN number that transforms a work from fan fiction into historical fiction? I'm curious to hear what others think.
(While you're at it, Mr. Updike, could you write another Rabbit book? Pretty please? Even if you have to call it Rabbit Remembered Redux.)