I read Communion and found it very interesting. While I don't believe a word of it, reading a book so coherent by someone who is either somewhat deluded or completely out of his tree is a very odd experience. I actually find Communion a much more effective horror story than most horror novels: it's got a nightmarish, disjointed quality, where weird things happen for no clear reason.
Some while ago I got talking to an expert on the paranormal - not a professional debunker, but someone who considers what he's told and on the evidence believes very little of it. He said that the most boring explanation (mental issues aside) for Strieber's experiences would be that he had been abducted by aliens. The modern UFO story, he said, read like a cross between bad 50's SF and old myths about the fairy folk, and it would be interesting to know why people through the ages felt a need to have that sort of story.