Some sources refer to Keel's book as a work of non-fiction, which would appear to be the same as labeling The X-Files a news program. In brief, the "facts" around the Mothman phenomenon are these: For about a year and a half, from the summer of 1966 to late 1967, various residents around Point Pleasant, West Virginia, claimed to have seen a humanoid creature, about 7 feet tall, with red eyes and large wings. He would often contact people while they were in their cars or looking through the windows of their homes; it was claimed his presence could disturb nearby TV reception. An editor at The Associated Press came up with the name Mothman, the catchiness of which assured further publicity for the alleged "creature." In December 1967, the area was struck by a real catastrophe--relating the details would spoil the film's ending--and Mothman either disappeared or greatly curtailed his public appearances afterward.
Director Mark Pellington and screenwriter Richard Hatem have taken great liberties with Keel's book, leaving out the homosexuality and the divorce and the illegitimate child and... No, wait. That was A Beautiful Mind. Nonetheless, they essentially use Keel's book as little more than a jumping-off point for a feature-length X-Files or Twilight Zone episode. At a certain point, you begin to wonder when the hell Scully and Mulder are going to show up.
Pellington's first film was the interesting coming-of-age saga Going All the Way, which was followed by Arlington Road, a film that nullified its best elements with a truly idiotic ending. Mothman Prophecies has similar problems and virtues: It may be stupid, but it's also effective in many ways. And Gere is a wise casting choice: He manages to convey utmost sincerity--not a trace of campiness or irony here--without making himself look like an idiot.
It's hard to know whether Pellington actually thinks this is nutritious food for thought, as the film sometimes seems to suggest, or whether he recognizes it as the fairly tasty, but empty, snack that it is.