To start off with, yes, I read books — I just haven't happened to have read any of the nine Stephen King novels which make up his self-described "magnum opus", The Dark Tower. So in this case, it's one of those occasions without any particular background perspective beyond what I've seen in the trailers and the fact that King fans had no lack of opinions on the matter.
The film stars Tom Taylor as Jack Chambers, a young boy who has recurring visions of a gunslinger, human skin-wearing creatures, a Man in Black, and children being kidnapped and strapped into an alter that drains energy from them and fires it against a looming dark tower. While his mother, Laurie (Vikings' Katheryn Winnick) tries to be understanding, his stepfather does all he can to push Jake out of the house and out of the way as quickly as possible. Eventually, the creatures from his visions show up, and the chase is on.
If you made a drinking game out of every time you find a trope in this film, you'd be plastered halfway through the film's rather meager 95 minute running time. The Dark Tower is a structure of unspecified origin and its existence keeps legions of evil and demons held at bay at the edge of the universe. There is also a multiverse, where differing worlds (which seem to be variations on a theme of Earth) all exist, and gateways (read: Stargate-like doorways that jump between 'verses rather than across distance).
Ruling over many of these realms is a Man in Black, whose real name is Walter Padick (played by Matthew McConaughey). He's the one that's been behind the kidnapping of the children and using their psychic energy (called Shine) to pummel the Tower. He's a personification of evil (though called simply a sorcerer who uses spoken words to commands others to do things like "stop breathing", "kill each other" or "burn").
Roland Deschain, played by Idris Elba, is the last of a group of Dark Tower defenders called gunslingers. The Gunslinger comes across as a blend of a monk, a knight, and a jedi; able to perform incredible feats of shooting accuracy (and with fast-healing as an added bonus).
The pieces all come together with the feel of an introduction to the world and its mythos, but we never really get to connect with any of the characters. Walter is a pretty solid personification of evil, but beyond watching in which messed up way he'll off the next person that crosses or fails him, we still don't really care. The impression I had walking out of the movie was that I would love to watch more and to see more of the universe, but that's the feeling I'd expect from a new series on Starz or Netflix. Not something that will now take a few years to get another installment. By then, any passing curiosity would have been long forgotten.
The last thing you want to create is a franchise opener that will be forgotten within a few months. At least Universal's Dark Universe first installment, The Mummy, will be remembered for how bad it was. Something like The Dark Tower is so middle of the road, there's nothing to really capture me enough to either want to read the books, or eagerly await the next movie.
Sure, it's cute that the psychic energy that's being sought which Jake is so infused with is referred to as the Shine (no, it's not midichlorians, but it might as well be). If folks recall, the Shine is the source of the title from the Shining — where Danny Torrence's visions are giving to him via his own Shine. King now describes many of his various works as sharing a single universe, but it's a bit overgenerous; the reality is he tends to only have one bag of tricks, terms, and monsters that he keeps going back to.
Director and co-writer Nikolaj Arcel did his best it seems to lay the groundwork, but the end result wasn't enough to hook those of us unfamiliar with the world.