Please pardon me if this has been discussed previously. I just became a member of this site & this is my first post. First off, I've been reading Stephen King (Richard Bachman) for years & I've read almost every non-fiction work he's produced (including "The Ledge" published in Playboy many years ago). I've thoroughly enjoyed reading all of them, even though you can count me as one of the disappointed over the way "The Dark Tower" series ended.
This was another great SK novel ... however, let me point out that changing the past is totally impossible ... even if we had the ability to travel back in time. Before the hordes devour me, let me explain why:
"If I could travel back in time & kill someone as the novel describes, I could also kill my own mother before I was born! But then I would never be born so I wouldn't exist to travel back in time to commit the murder. Therefore, as a physicist (no, not Sheldon Cooper) & a fantastic singer, I have to conclude that changing the past is impossible."
Now traveling forward in time & changing the future ... that's an intriguing idea & I can't prove that it's impossible. In fact, I believe it's quite possible.