“The Dark Tower,” the long-awaited arrival of Stephen King’s beloved sci-fi/western/horror novel series to the big screen, lands as a serviceable action-adventure, thanks in great measure to the casting of actor Idris Elba.

Elba’s charismatic presence, plus a few of the film’s set pieces and its light touch in terms of referencing its source material, all result in a film that at the very least is accessible to audiences who come in cold as far as knowing King’s body of work.

Longtime fans, meanwhile, can take pleasure in Elba’s take on King’s central hero in the series, the Gunslinger, and look forward to his return in future films.

What’s it about?

“The Dark Tower” begins with New York City teen Jake Chambers (Tom Taylor), who struggles with vivid nightmares he transcribes into sketches that cover his bedroom walls. Repeated images in his drawings include a man with a western-style revolver, a man in black, and an immense tower reaching into a sky dominated by two moons.

His loving mother Laurie (Katheryn Winnick) and stepfather Lon (Nicholas Pauling) have Jake in therapy for what they believe are just dreams. But Jake believes differently – not only are the dreams somehow real, but they’re connected to strange earthquakes happening all over the world.

Of course, Jake’s right. Roland, the Gunslinger (Elba), Walter O’Dim, the Man in the Black (Matthew McConaughey), and the Dark Tower are all real, and all tied to an unending cycle and an eternal battle of good and evil.

Jake eventually learns he has his own role to play in Roland’s battle with Walter, a battle that could plunge the universe into darkness and fire should Walter achieve his ultimate goal: the Dark Tower’s destruction.

But to save the Tower and all the many worlds connected to it, including his own, Jake must help Roland overcome foes more powerful even than Walter or the Crimson King he serves – grief and despair.

Another trip around the wheel

Something that may comfort fans of the “Dark Tower” novels is the choice by the film’s production to avoid trying a straight adaptation of one or more of King’s original novels into a film.

Rather, “The Dark Tower” film ostensibly serves as a sequel of sorts to the novel series. Screenwriter Akiva Goldsman’s script can be interpreted as picking up where the final volume of King’s novels left off, with the Man in Black once again fleeing across the desert, and the gunslinger following in a new cycle.

That said, there’s plenty in Goldsman’s screenplay that’s directly adapted from King’s novels, including many Easter eggs referencing non-Dark Tower King stories. In that sense, there’s fun to be had for longtime King fans in seeing those allusions brought to life organically within the film.

All about Idris

Any appeal “The Dark Tower” might have outside of hardcore fans of the novels comes mostly by way of Elba. He’s simply impervious to “uncool”, and thus is the perfect choice to play King’s spaghetti western-inspired hero.

McConaughey, on the other hand, doesn’t seem to put a whole lot into his turn as Walter. To be fair, the production doesn’t seem to demand much from him – they dress him up in impeccable black, tell him to tame his Texas drawl and whisper his lines with as much malice as he can muster, and let him go.

As for young Tom Taylor, he’s solid as Jake, but he’s not given much to do once the mystery of the dreams is “solved” aside from being a somewhat typical action movie young sidekick.

Worth seeing?

Truth be told, there’s not a whole lot of depth to any of the characters here – Roland is angry, Jake is troubled, and Walter is a villain with a soft spot for his most implacable enemy.

That absence of depth results in a film story with little emotional impact. Sure, the fate of the universe is at stake, but when isn’t it when it comes to stories like this? All apocalypse rising-themed stories being equal, what then matters are the characters at the heart of the battle – if they aren’t interesting or engaging, then who cares?

That relative lack of character depth doesn’t doom “The Dark Tower” or its entertainment value. It still has its moments of fun, and again, fans of the Gunslinger should be pleased at least with how Elba brings him to life.

But it doesn’t help the film stand out from the summer’s lineup of franchise blockbusters, either. When considered alongside this summer’s most entertaining genre entries, “The Dark Tower” simply doesn’t reach high enough.

The Dark Tower

Starring Idris Elba, Matthew McConaughey, Tom Taylor, Claudia Kim, Fran Kranz, Abbey Lee, and Jackie Earle Haley.  Directed by Nikolaj Arcel.

Running time: 93 minutes

Rated PG-13 for thematic material including sequences of gun violence and action.