My husband has a degree in film from NYU (go ahead, ask him how useful it is!), so he has a few texts hanging around--including Noel Carroll's fantastic The Philosophy of Horror.
I haven't indulged in academic writing in a while, which is a roundabout way of saying this isn't general-audience-easy to read: but it's worth the trouble indeed, for anyone interested in the horror genre and by extension the way that fiction works from a philosophical perspective. Carroll spends a lot of time of both the paradox of fiction, i.e., "How can something cause a genuine emotional response in us when we know it's not real?" and the paradox of horror fiction in particular--"Why on earth do we read/watch things that frighten and disgust us?" These chapters (2 and 4) are the most abstruse; Carroll admits in his introduction, "[Chapter Two] is the most technical chapter in the book; those who have no liking for philosophical dialectics may wish to merely skim it, if not skip it altogether." (Isn't it nice when an author gives you permission? I had forgotten my love of said dialectics until I fell back into the comforting style: "X theorizes this. But that doesn't work because of Y and Z...")
Chapters 1 and 3 are the empirical heart of the book, and the ones that will stick with me as I consume artifacts of the genre, and related ones like sci-fi/fantasy--currently, this means that during my daily binge on Supernatural, part of me checks off Carroll's criteria. First, he defines and refines the concept of art-horror (distinguished from feelings of horror elicited by real-world events), and what's required of a "monster" to be an object of this emotion. They must be threatening, obviously, but further, what he calls "impure." The latter term borrows from anthropologist Mary Douglas, who explained the impure as things that fall in between or cross the boundaries of cultural categories, creating contradiction from which we recoil. The easiest example of this is things like ghosts or vampires, who are both living and dead; but Carroll ticks off many other types of transgressive monsters: combinations like werewolves (man/beast) or China Mieville's khepri (woman/scarab); magnifications like the radiation-embiggened critters of 50s sci-fi; the incomplete, crawling hands and eyeballs and formless blobs. He argues persuasively that the fundamental feature of art-horror is cognitive threat; we react to these interstitial creatures with not only fear but revulsion.
And in chapter 3, he analyzes recurring features of horror plots--not denigrating them as formula, but teasing out the way that many stories work, in order to understand how they're satisfying. He characterizes the most common structure as "the complex discovery plot," which consists of four phases: onset (the monster begins to affect the human world, generally by killing people), discovery (the protagonist[s] begin to understand that this threat is unnatural, outside their usual experience), confirmation (often, they must convince an authority of the nature of the threat, overcoming initial resistance to the supernatural explanation), confrontation (what the Winchesters would, constantly and puzzlingly, refer to as "ganking" the monster). Of course, these four phases can be shuffled around and repeated and recombined, and some stories only use two or even one (all onset! all confrontation!). It's an absolutely marvelous theoretical framework, elegant and precise and extremely convincing.
And, you know, a great excuse to read some Joe Hill or watch some horror movies. For research.