Before I start I will note I have not read the books (will change that when I get a chance).
The first and most important thing that The Dark Tower did was to built a large and complex world(s) without being an info dump or sacrificing everything else to do it. When needed it even let you just absorb the scenery. It reminded me of Guardians of the Galaxy Volume One in this respect.
The plot was not huge and complicated. While all the necessary bits were there many of the why’s were not explained. Honestly I am okay with that, if I can think of several reasons for an action and which one is true does not matter then I don’t really need details. The movie does that several times for several things. I like the idea that the movie respects me enough not to feel the need to spell everything out.
The action was good, I really liked the way they showed Roland’s gunslinging, he could do ridicules bullet bouncing and such but nothing too out there. He did nothing that could not in theory be done if you were good enough and had enough information (unlike say curving a bullet).
They also showed the man in black’s magic well, it was consistent and logical the way he used it. He was far from all powerful but he was smart and knew his limits.
The final fight was made much better because of this, it would have lost all its punch otherwise.
I will say that main character wise the movie does look to be of two minds, it seams to flip between Jake (the kid) and Roland. This does not hurt the movie as much as you would think but it does make me wish the movies was a bit longer to allow for more development.
As far as characters go one thing I did not realize until after I left the theater was that Roland treated Jake as an adult. There was no cliché having to prove himself an adult phase.
I really did like the movie, even if I think the characters could have been developed more. Its worth seeing just for the interesting and vast world it shows, let alone everything else.