In 1988 James Cawthorne and Michael Moorcock compiled Fantasy: The 100 Best Books — which was more a list of books that had influenced the development of the modern fantasy genre, starting with Gulliver’s Travels (1726) and including a number of important but not-so-good works, like The Castle of Otranto (1765):
There are novels so fundamental to the development of a particular genre that the question of their literary merit is of secondary importance. Horace Walpole did not invent the basic constituents of the Gothic novel, but in The Castle of Otranto he combined them in a manner which became a standard formula for the next two centuries. It was the publisher’s equivalent of sliced bread. Their readers took to its clammy horrors with delight, and in growing numbers as the ‘penny dreadfuls’ set out to wring the last drop of ichor from its lurid lexicon.
(Let me stop to note that my spell-checker doesn’t recognize ichor.)
By then, the Gothic had travelled far from its original sources of inspiration. The prevalence of castles in the literature was no accident, nor was the frequency with which they were built on the iceberg principle, with nine-tenths of their structure consisting of subterranean vaults. These spectre-infested spaces were rooted in the fantasies of an architect, Giovanni Piranesi. A revised edition of his Carceri d’Invenzione appeared in 1761, featuring a series of drawings of prison interiors conceived on a titanic and overpowering scale.
Walpole, who had already converted his Twickenham home into a mock-Gothic castle, took from Piranesi the central image of his novel, a black-plumed helmet of monstrous size. Around it he gathered the now familiar cast of wronged and lovesick maidens, unhinged and tyrannical nobles, younger sons of ancient families travelling incognito.
The Gothic novel obviously became a tired cliché — but I doubt most people today have read a single Gothic novel. The bad-but-classic Universal horror films include some of the elements — namely the castles and the rare Carpathian armadillo — but even those passed profoundly out of style long, long ago.