As I've said before, Isaac Asimov has long been one of my favorite authors, from science fiction (of course) to science fact to history to mystery. But his fantasy falls flat, at least if judged by Magic: The Final Fantasy Collection, which I finished reading today.
Asimov is fond of quoting Arthur C. Clarke's assertion that any sufficiently advanced technology is indistinguishable from magic; this may go far to explaining why I find his fantasy unsatisfactory. He is all-rational,* to the extent that even his demons and his dragons seem mundane. There is no magic in his magic. Some of the tales are good stories, but they lack the sparkle, the wonder, the life of a good fantasy.
Interestingly, Asimov had great respect for J.R.R. Tolkien as a writer and read The Lord of the Rings at least five times. Since I consider Tolkien to be a master at the elements that I find lacking in Asimov's fantasy stories, I wonder if those aspects of the LOTR, which in my opinion make it the monumental work that it is, were invisible to him.
Perhaps they were; certainly there is enough depth to the story to attract people on many different levels, as the makers of the movie version proved. Or...perhaps...he did catch a glimpse of the book's magic, which continued to draw him back, though he didn't know why.