Re: I wonder
Frank Herbert -- and the abomination that has happened since.
Anne McCaffery -- and the even more complete abomination that is her son.
The F. Herbert ones were also mostly son follows up...I still don't believe where the story ended up was where Frank would have taken it, never mind the glaring lack of deep wisdom the sequels have compared to the Masters works.
I thought the Brian Sanderson completion of Wheel of Time was rather seamless - I appreciated not being left hanging in when Robert Jordan departed before finishing.