Ladies and gentlemen, may I remind you that other people writing books containing a famous author's characters are, by definition, fanfiction authors. Few, if any, write anything of compelling quality, and let me remind you that most take the story in directions the author would not have approved. Remember Scarlett by Alexandra Ripley? Not only did Rhett and Scarlett supposedly get back together, but Scarlett became the head of a clan - yes, clan - in Ireland. Margaret Mitchell would never have written anything resembling that. The author basically wrote a numbered-series romance novel and used Mitchell's characters' names.
So please, please, if you really want to read something like Jane Austen's Pride and Prejudice from something like Mr. Darcy's point of view, read Henry James' Daisy Miller, all right? E. M. Forster's A Room with a View will also do.