After completing "Escape From L.A" (1996), John Carpenter was actually thinking of taking a break from the movie business. For him, making movies "stopped being fun". He couldn't decide whether to quit or not. Then he got his hands on the novel βVampire$β & two screenplays (by Don Jakoby and Dan Mazur) based on it.
He took them home, read them & found it interesting. He combined the good parts from all the three works & included his own vision. And the idea of making a Horror-Western, combining Hawks and Peckinpah intrigued him. So, he made "Vampires" (1998).
(John Carpenter's interview with Anthony C Ferrante, Dreamwatch Magazine, 1997, & John Carpenter's interview with Jim Hemphill, Filmmaker, 2015)