If one definition of a really good book is one for which readers want a sequel, then it's not surprising that sequels have been written by lesser-known authors for several of my favorite old classics. Gone With the Wind has been one of my favorite novels since I first read it as a teenager. Almost 20 years later, Scarlett by Alexandra Ripley was published and my sister gave it to me for Christmas. As a novel it was adequate, but never something I would read more than once. As a sequel to Gone With the Wind, it was a huge let-down. Scarlett was suddenly more sensitive and conscientious, less greedy and manipulative, and the reconciliation between her and Rhett (the real reason anyone wanted to read it) was underdeveloped and unconvincing.
Since then I've read several sequels to Jane Austen novels with similar reactions. One sequel to Mansfield Park really annoyed me. Although she did an admirable job imitating Austen's style, the author had the nerve to make Henry Crawford into a hero and changed the details of the original ending, so that his affair with Maria Rushworth was really just a big misunderstanding. I'm sure many readers liked Henry more than Edmund and wished Fanny had married him, but in my opinion it requires massive conceit to try to rewrite anything as brilliant as Mansfield Park.
At least P.D. James did nothing to undermine the beauty of Pride and Prejudice. Her murder mystery Death Comes to Pemberley takes place on the Pemberley estate six years after the marriage of Darcy and Elizabeth. It includes many of the original characters, including Jane and Bingley, Wickham and Lydia, Colonel Fitzwilliam and Georgiana, adding other characters as might be expected. She creates a suitable tone for the novel, less humorous and more mysterious. Most importantly, the characters and details of the story remain true to the original. (The worst inconsistency that I noticed was her statement that Wickham was not welcome in the Bingleys' home, whereas Pride and Prejudice states that he visited there frequently.)
Although the novel could be called a murder mystery, it departs from the genre in several significant ways. The main characters, notably Darcy and Elizabeth, aren't involved in solving the mystery in any way. In fact, the guilty parties come forward at the end and make voluntary confession, begging the question of why they didn't do that in the first place and save everybody the hassle. Darcy and Elizabeth, and by extension, the reader, are merely spectators of the whole show, giving the story a passive feel. Several secondary plots could have been developed more to make the story more interesting and add romance.
But the book was an interesting picture of life on the Pemberley estate and the marriage of Darcy and Elizabeth. It provides closure for a few of the secondary characters of Pride and Prejudice while creating clever connections with characters from Persuasion and Emma. For Austen fans, it was a nice read. Of course, it falls far short of the wit, humor, and insight of her own novels.