Have you read The Girl with the Dragon Tattoo books? I have, a while ago, and loved all of them. I didn't know the tragic story of Stieg Larsson's death (he had a heart attack and passed away before the books were published and became a success).
Now the fourth book will be written by a different author, based on the unfinished draft (or so it is rumored). It made me think...would you want someone else to finish writing your book in case you died? Or would you turn in your grave if they did?