Sorry, thought it was evident.
Sometimes adapted screenplays hit all the right notes. Even though GoT is a TV show, Seasons 4 and on have phenomenal adaptations even though they take from different parts of the books and even different books! Some movies you sit though and come out of in awe. Others you need to ruminate on the story, structure, thematic material, and inferences/metaphor/allusions and then you realize that it was a masterpiece. That being said....
I've read all the books in the Dark Tower, some multiple times. I know it would have been 100% impossible to incorporate all the themes into one movie. However, as stated above, there are ways to do it with proper screenplays. Probably not in a singular movie, but I know it could have been done so much better. This movie was devastatingly horrific. It missed practically everything from the books! Honestly, I would give it a 0/10 if I could, but alas it gets a 1 from my IMDB account. Elba's was awful, not capturing the essence of the gunslinger at all. Again, the books are masterpieces with Roland truly last of his kind. Pick any actor they could have done a better job I bet.
I could go on and on, but I can't waste my time on this drivel.