Just finished rereading Roger Zelazny's Amber books (still have the last short story to go). Read it many years ago, but recently bought the ebooks (sometimes at midnight--need next book!) Still love them--all ten. It is clear from the ending of Prince of Chaos, and from the short stories, that he had more books planned, but he died a couple decades ago, at the age of 58, and so we do not have them.
I morn the books we didn't get, but would not have wanted to hear someone else's voice in my head, telling those stories. Gone too soon.