In-re to my previous post here, some science fiction authors were not skeptics, indeed, were Forteans. The UK's own Eric Frank Russell 91905-1978) was on record with Fort as his favorite author, and did the non-fiction work Great World Mysteries in 1957. Wilson "Bob" Tucker (1914-2006) was another, although he kept his more "serious" interest relatively quiet, but both men often used Fortean Themes in their fiction. I would simply advise those here with an interest in science fiction to be cautious if/when dealing with sf professionals, for, as likely as not, one will be accused of suffering some mental disease or the psyche, or the like, if a belief in cryptids, or UFOs, or what-have-you is expressed.
As for John Keel himself, he has always had a devoted group of followers, I suppose we can say, and I enjoyed his books myself, although I cannot call myself an actual fan. I suppose Strange Creatures from Time and Space (1970), and The Mothman Prophecies, (1975) are my favorite titles of his, all the same. One of his later books, The Complete Guide to Mysterious Beings (2002), sounds quite interesting, although I am unsure if it is largely reprint material? Keel was a regular columnist for Fate magazine for a time in the 1990's, when this magazine had switched fro several years to a large-size format, an unsuccessful effort to increase sales (it is "digest-size once more). The title went through what seemed a some "new age-ish" period then which may have turned-off some, just as a guess on my own part.