WARNING: right from the off this post discusses HUGE spoilers from essentially every book! BE WARNED!!

There are few things that divide human kind quite as much as the ending to the Dark Tower. Love it or hate it, you have to admit it was unexpected and then, likelier than not, go on to ask a question... why? Why did it have to be that way? Why the deaths of Jake and Eddie? Why the breaking of the Ka-tet? Why the apparent failure of the quest, with Roland realising the nature of his eternal torment just that bit too late? Why the meta Stephen King plot line? Why was it so important for Roland's Ka-tet to save King in the Keystone Universe from his car accident so he could write the books, when in our own universe King got hit by the car in 1999 and wrote the books anyway? I would like to suggest an answer for all of these occurrences, one that I haven't seen discussed elsewhere online, and for that answer first we have to put down the books and look at our own reality.

It is important to first make clear- our world is not the Keystone Reality in the books. There are too many deliberate differences, from the location of Co-Op city, to the lack of a Tet Corporation in New York. A major difference is that in our world King was not shoved by Jake in 1999, he was in fact hit by the car with no rescuer. This means that our King is not of the same timeline as the Keystone Earth King. And in our world, the one where King was hit by the car alone, we ended up in a reality where he writes that everyone dies and Roland seemingly fails. Like it says in the books, by writing that reality, King creates that reality. In our world King gets hit by the car alone and creates a reality where Roland apparently fails... but also where, unlike in our reality, Keystone King is touched by Ka and helped by Jake. A reality is created where Keystone King still goes on to write the books, only who's to say he writes them the same as he did in our world? Keystone King has met his own characters, saw that they were real and living, and they did something amazing for him- as far as he knows they saved his life. It seems to me that something like that would influence a writer to change his original, more macabre, ending plans...

It is my theory that the Keystone King in our books, the one who experienced the attempted rescue by Roland and his Ka-tet, wrote a different version of the Dark Tower- he created a different reality. Thanks to Roland and Jake mounting their rescue, Keystone King was touched by Ka and created a reality where Roland succeeded in his quest and none of his Ka-tet died. This means that, in Keystone King's books, Jake wasn't there to give his life in an attempt to rescue the King in his story, there was no need for the Tet Corporation to protect the Rose as the Tower was rescued, and the books still got written by the Keystone King's version of King only following his car accident and without the assistance of Roland and his Ka-tet. And if you think about it, this sequence of events is pretty familiar, because it is the sequence of events as we see them in our universe. Keystone King from the books writes our reality, and in our reality Roland, his Ka-tet and the White, won. That is why it was so important for Roland and the team to rescue Keystone King and have him finish his version of the books.

If you thought it was complicated so far, this is where it gets really mind bending. In Keystone King's books (the books within our books) Roland succeeds and our own reality is created in which the Keystone King's version of King (our King) writes the story of Roland's penultimate loop- the books as we know them where Roland fails and the Ka-tet is broken. But by creating that "bad ending", the Keystone King's version of King (our King) also creates the Keystone Reality as it appears in our books, where the Keystone King was helped by his friends during the accident, saw they were real and living in a highly visceral way, and went on to write and create our own universe where Roland succeeded. It is a never ending loop, a cycle of each hand drawing the other. It sounds impossible, it sounds like kaka, but then they do say Ka is a circle.

To put it another way- as it says in the books King writes and creates the multiverse, but the next loop is always the one that the King from the previous loop writes out. Roland can never change his own loop, but can alter the next by his varying interaction with King. In the loop that sees Roland's Ka-tet broken, King gets touched by Ka, there is an attempted rescue and events are as we see them in the books (the Keystone Reality). In the loop that sees Roland's success, King does not get touched by Ka, but hit alone by A car (excuse the pun), and events are as we see them in our reality. Our King creates the books King, who creates our King, who creates the books King, and it goes on and on.

This theory also explains the apparent changing authorship of "Charlie the Choo Choo". We know Jake is from the Keystone World, as he discovers the Rose growing in the vacant lot, a Rose that only grows in one reality- the Keystone Reality. When Jake finds "Charlie the Choo Choo" the author is listed as "Beryl Evans", however later on in the Keystone World the author is listed as "Claudia y Inez Bachman". In my theory it is "Claudia y Inez Bachman" who is the actual Keystone author of the book, and this is actually a pseudonym for the Keystone King who was touched by Ka. "Beryl Evans" appeared as the author on the copy of "Charlie" that Jake found in his bookstore because this copy came from a different universe, and was placed there by Ka order to help Jake later on. This is why, in our world, "Charlie the Choo Choo" is not written by Bachman, as our version of King wasn't touched by Ka but A car, and wrote the "bad ending" version of the books after his accident. Keystone King on the other hand was touched by Ka, and therefore took the place as the conduit to write Charlie as well.

All in all, this means the reality where Roland succeeds can never contain the story documenting that success. In our world Roland succeeds on his quest, but without the story as we have it, that success could never have been reached. If we wanted to read the story of Roland's success, the story of our own world, we would have to go to the Keystone Reality where Kings creations attempt to save him during car accident, but also where everyone else dies and Roland fails.

I for one am happy here, with the ending we may not want, but the one we need.