Trying to turn the sprawling world of Stephen King‘s “The Dark Tower” into a digestible narrative for the big screen is no easy feat, and while the author himself has signed off on the upcoming film, even he doesn’t guarantee it’ll succeed.

“They sent me a number of different drafts and it came into focus, let’s put it that way,” he told EW. “I’m 100 percent behind it — which doesn’t mean it necessarily will work, just that it’s a good way to try and to get into these stories.”

Helping to bring “The Dark Tower” to a mainstream audience are Matthew McConaughey and Idris Elba in the lead roles, but fans might be wondering just how they’ve tinkered with the story in the transition to the movies. Well, it seems those who have read the books will have an interesting perspective. “The hardcore fans of The Dark Tower series will know that this is actually a sequel to the books in a way,” director Nikolaj Arcel said. “It has a lot of the same elements, a lot of the same characters, but it is a different journey.”

After years of delay and waiting, those hardcore fans finally get to see a glimpse of Arcel’s take on the series with the full trailer. Watch it below. “The Dark Tower” opens on July 28, 2017.