The Mothman Prophecies

From Wikipedia:
The Mothman Prophecies is a 1976 book by parapsychologist John Keel, described as nonfiction.

The book's subject matter mostly concerns events in Point Pleasant, West Virginia, during 1966 and 1967, focusing on sightings of a creature dubbed Mothman. It also includes Keel's theories about UFOs, Men in Black, ghosts, and other paranormal phenomena, as well as the December 15, 1967, collapse of the Silver Bridge across the Ohio River from Point Pleasant to Gallipolis, Ohio.

The veracity of the events described, especially those said to have been witnessed only by Keel himself, cannot be further established beyond reasonable doubt.

The book was the basis of a 2002 film of the same name.