Dean Koontz is not one of my favorite authors. Most of the books of his which I have read have been promptly donated or sold. That said, "Fear Nothing" and its sequel "Seize the Night," are among my favorite books.
Other reviewers have laid out the plot points, so I will only say that Koontz has created four memorable characters in these books, given them a storyline which is chilling and different, and made the whole experience entrancing. I will also say that Chris Snow's attitude towards the XP is one I have remembered and tried to achieve myself with my MS.