King's novel is deeply flawed. It begins as a deftly written, very personal story, with so much promise, and then ... goes off the rails in a way that almost ruins the whole thing. There really is no better word for what happens after the midway point of the novel than sloppy. Kubrick was wise to go in a different direction. He tells a gripping story that works on many levels, and avoids King's big mistakes. It's not my favorite movie, but it a better realized story than the novel.
Based on that trailer, if a film festival can't be bothered to watch this film, then all is lost. Great trailer. Great subject. Congratulations on your (obvious) talent and hard work.