Salem's Lot by Stephen King
Throughout the entire novel the main theme was belief. obviously there were two sides, you either believed or you didn't, that was vital to survival for some characters. Belief serves as "protection" for some characters, but it also led to the downfall of others. The characters the believed in the actual existence of the vampires and the ways to fight them off survived the longest in the novel. This is why the theme of 'belief' was important.
Setting was very important in the novel, because the main character Ben grew up in Jerusalem and made his way back in adult hood to write another novel. Also because of the homicide and suicide in the Marsten house, this one one of the reason Ben made his way back because he tried to rent the home, in hopes it would ignite something in him to help him write another novel. So the house in the story had a big role in the novel.