In the Mouth of Madness (1994) on Netflix

The efficient and skeptical freelance insurance investigator John Trent is hired by the publisher Jackson Harglow to find where the famous writer Sutter Cane might be. After writing a series of best-sellers in the horror genre, affecting the reason and causing disorientation, memory loss, and paranoia in readers, Sutter has simply vanished near the release of his new novel, "Horror in Hobb's End." There is mass hysteria of his anxious fans waiting for the new release, and John believes that his disappearance is a marketing strategy. John follows his instincts and travels with Cane's editor, Linda Styles, to New Hampshire, seeking for the apparently fictional town of Hobb's End. While driving along in the night, Linda reaches Hobb's End, and John discloses that Sutter Cane has unleashed a powerful evil force in the black church of the mysterious town, and his twisted imagination is changing the reality and perception of those who read his novels.