The gothic is an avant-garde genre

…the gothic is an avant-garde genre, perhaps the first avant-garde art in the modern sense of the term. A pursuit, half serious enterprise, half fashionable vice, of the intellectuals of the end of the 18th century, it remained highbrow enough to tempt the Shelleys and Byron, for instance, to try their hands at it. The popular success of Frankenstein, perpetuated still in movies, and known in its essence to children in the street, obscured the fact that it was launched as an advanced book; and that it belongs to a kind, one of whose functions was to shock the bourgeoisie into an awareness of what a chamber of horrors its own smugly regarded world really was. If some examples of the early gothic strike us now is comical, this is only in part the result of changing taste; such books were from the beginning intended to be, in part at least, a joke on the middle class reader who would inevitably find them too funny or not funny enough!

From Leslie Fiedler’s Love and Death in the American Novel (1960).