Is there a way to get a complete Stephen King set with all (or most) of the books he has written?

You can get a lot of his collections of books but not all in one set. The Gunslinger series has four alone and the Green Mile has many also. There are about 119 books that he has written. This site has them all by rating.

Best of Stephen King (119 books) - Goodreads

www.goodreads.com/list/show/309.Best_of_Stephen_King