Diagnosed with Alzheimer's in 2010, Pratchett has curtailed a lot of his traveling and interviews. He has donated lots of money to Alzheimer's research as well the protection of orangutans (as one of his recurring characters is a man who was transformed into one).
In this fourth book in the Tiffany Aching arc, Tiffany travels to the city of Ankh-Morpork for part of the book, and meets a few other recurring characters from the Discworld. And one other character she meets has only appeared once before, and it's one that I as well as many other readers have always wondered about. What happened to her?
Now we know.
And with other things mentioned, I feel Pratchett is doing his best to wrap up loose ends, move bits of continuity along, and prepare to close the door on his universe. And I for one hope that he gets the opportunity to finish his work.
There are many authors out there who have died and left their works unfinished or open to interpretation.
The first posthumous speculation I ever read was Fuzzy Bones by William Tuning which continued the story about Fuzzies introduced by H. Beam Piper. Then I found the true lost sequel written by Piper that was found after his suicide.
I've read the Dune sequels and prequels and will read the "inter-quels" as they come out. Written based on notes and manuscripts by Frank Herbert, these books are written by Herbert's son Brian and Kevin J. Anderson. Now while I enjoy the books and knowing the rest of the story (as Paul Harvey used to say), they don't have the same gripping story as Frank Herbert would have written them.
Another person carrying on from a passed writer based on notes left behind is Brandon Sanderson working to complete Robert Jordan's Wheel of Time series. I've enjoyed Sanderson's stories, mostly because he is closing the story and moving the plot along. Jordan had found a cash cow and said a few years before he dies that he intended to write until he died and for someone else to complete his story for him.
Then there is the sixth book in Douglas Adams' Hitchhikers' series ... And Another Thing by Eion Colfer. I read this one, and it was severely lacking in the Adams' touch.
And finally there are the Amber prequels written by John Gregory Betancourt. I can't even bring myself to read them. The Amber Chronicles by Roger Zelazny are some of my favorite stories, and I don't want anyone's speculations to mess with the memories I have of them.
So I thank Pratchett for his wonderful world, and wish him continued strength in his life, but hope that he has time to finish his works.