An interesting novella written by the Liverpudlian author Clive Barker in 1988.
Aaron Boone is a brooding young man plagued by visions of monsters and murder. Searching for answers, Boone discovers a secret underworld populated by the last examples of a dying breed of monsters known as the Nightbreed.
Soon the Nightbreed are hunted down by Boone's psychotic psychiatrist and a bunch of rednecks and, as is typical of Barker's writing, we are led to question who are the real monsters; the Nightbreed or humanity.
Also made into a visually stunning horror film "Nightbreed" (1990) by Barker starring Craig Sheffer as Aaron Boone and director David Cronenberg as his psychiatrist. Watch out for cameo appearences from Stephen King and Clive Barker himself.