Gothic is a bit like that old pornography rubric: I know it when I see it. Dracula? Gothic. King Kong? Not Gothic. The Cure? Gothic. Metallica? Not Gothic. Gothic isn't just the monstrous, or the dark, or the nihilistic. It is ruined structures. It is shadows. It is urbane yet corrupt. It is beautiful and ugly in such close proximity that it is impossible to decipher which specific features are beautiful and which are ugly. Robert Smith tripping on acid with his jet-black bird's nest, smeared lipstick, and vulnerable pout is Gothic. James Hetfield guzzling Bud in denim is not.
Roger Luckhurst keeps his definitions much more specific and academic in his new book Gothic: An Illustrated History. Yes, he agrees that Gothic involves ruined structures, monsters, and blurred borderlines, but he has no problem defining King Kong or Godzilla as Gothic characters because they're monsters and monsters are Gothic. I don't know where he comes down on the big "Is Metallica Gothic?" question because he completely ignores Gothic music. He does address architecture, art, literature, design, and film, so Gothic: An Illustrated History, so it would be unfair to call the book limited, and the writer does cover these topics with authoritative command and novel organization: the chapters are largely organized according to locations, which allows a great deal of discussion of ethnicity and cultures, revealing the racism at the heart of a good deal of what might be considered Gothic. However, by ignoring Gothic music and fashion, Luckhurst leaves a major gaping hole in his book and fails to complete the definition he valiantly works to construct.
The illustrated format of Gothic would have also lended itself very well to discussions of Gothic music and style, since both of those strands are so closely entwined--after all, Robert Smith and Siouxsie Sioux are probably the Goths most Goths strive to emulate. There are no images of those two Gothic icons, but there are plenty of images of architecture, furniture design, fine art, and horror movie stills that make each turn of the page a thrill.