I am currently reading the 7 books of Stephen King's Dark Tower series (I've reached "Wizard and Glass"). When I started it, I had the impression it was a finished series and I didn't read very much about its ending to avoid spoiling myself.
I recently found out there will another volume in the series, The wind trough the keyhole.
Can anyone explain how does that fit in the whole series? I am interested if the first 7 had a satisfying ending, and this comes as an extra, or did it have an open ending?
What exactly happens in the 8th book doesn't interest me (yet), what I want to know is how "complete" the first books are and if Stephen King is only planning to enrich the universe with this future book (or even other books in the series), or to give Dark Tower a proper ending, where all the loose ends are tied together