At just 19 years old, Stephen King began penning an eight-part “The Dark Tower” series of novels that would take 30 years to finish — and three directors, as many studio changes, and over a decade before it made it to the big screen.

Was it the “tricky” task of adapting 4,250 pages of material that had become so beloved to fans — the obstacle cited by “Lost’s” J.J. Abrams, who, in 2007, first took a stab at it? Was it the lofty (and costly) ambition of Ron Howard, next director in line, to adapt it concurrently as a television and film series? (Howard is still attached as producer.) According to Oscar-winning screenwriter Akiva Goldsman, who remained onboard after Danish filmmaker Nikolaj Arcel took the helm in 2015, the problem was genre.

“This is part why ‘The Dark Tower’ novels are Stephen King’s magnum opus,” explained Goldsman at the film’s New York premiere at MoMA on Monday night. “They are liberal as they skitter across horror, science fiction, family drama, and that is much more acceptable outside of America, interestingly enough. But we like our genres in boxes.”

King’s story — about a mythical tower bridging many worlds, which “the Gunslinger” Roland Deschain (Idris Elba) strives to protect, and archenemy “the Man in Black,” Walter O’Dim (Matthew McConaughey) sets out to destroy — marries fantasy, sci-fi, horror, and Western elements. His main influence was Robert Browning’s 1855 poem “Childe Roland to the Dark Tower Came,” while King also references J.R.R. Tolkien’s “The Lord of the Rings” and Clint Eastwood’s “Man with No Name” character as inspirational.

But is America finally ready for this first film installment, and the television show that Goldsman and writer/exec producer Jeff Pinkner imply is forthcoming? “I think we’ve always had an appetite for things that bridge the genre, but we’re guarding our ability to accept it,” said Goldsman. “So ‘Stranger Things,’ for example, is a beautiful example of that sort of hybridized entertainment; Spielberg is sort of the king of it, ‘E.T.’ is that, ‘Close Encounters’ is that.”

The script was enough to intrigue McConaughey — who enjoyed throwing his conscience to the side and depicting “a lightning bolt of evil.” (“The devil’s in the ‘yeses,’ not the ‘nos,’” he cautioned the press line.) “The true fans are going to see, we left a lot of nuggets in there for them to see, that they’ll know about, that some people who didn’t read the books won’t know about, and at the same time, it lives on its own.”

Goldsman described the final, “pared-down” script — alarmingly pared-down to fans, who’ve questioned the 95-minute length — as quintessentially a father-son story: “a boy who is fatherless, and a man who has lost hope, who finds it in the eyes of a little boy.” It draws primarily from King’s first and third books (in which the Gunslinger makes futile and repeated efforts to reach the Tower), and serves both as a first installment and sequel to the series — which even director Arcel admits is confusing.

The director, who’s making his English-language feature debut, and who taught himself the language by reading King, said,” “It’s the heightened state of awareness for our hero, so that it’s his last journey through the adventure.” King also tweeted a photo of a long-lost horn, which the Gunslinger now carries, that was a hint to fans this might be Roland’s final journey to the Tower, disguised as his first.

But what does this eponymous “tower” represent in the first place? While King intended it be metaphorical, the answer depends on whom you ask.

“The Tower is that which we search for, which we can never find,” said Goldsman. “It’s the thing that is at the other end of your quest, happiness or redemption, forgiveness, a cold beer, whatever it is that spurs your heart and keeps pulling you forward.” A slightly more-optimistic Pinkner believes it to be “that thing which is unattainable, and yet, you go for anyway — it’s hope, it’s faith, it’s a reason for being.”

Arcel’s take was decidedly more spiritual. “If I were a believer, I would probably say [the Tower is a metaphor for] God, that sort of divine presence that protects the universe and protects us with light… ‘The Dark Tower’ is the perfect embodiment of that idea — that there’s something out there, whatever it is, that at least is trying to protect us. It’s not doing a very good job right now, but it’s trying.”

“The Dark Tower,” from Columbia Pictures and MRC, opens nationwide on August 4.