It's a living force in our culture, but when you go back to the original it's bad in all sorts of ways- badly written, badly constructed, badly plotted. It's a great idea indifferently executed.
Mary Shelley was still in her teens when she wrote it.
I think it's disguised autobiography. Shelley was married to a monster- the supremely egotistical, self-pitying, self-exiled, womanising, junkie poet, Percy Bysshe. Read "Epipsychidion"- in which he openly disses Mary- to discover the full extent of his mawkish, adolescent shittiness. Frankenstein is a depressed and depressing book and no wonder.
Maybe it would be forgotten, or at least pushed to one side, if it hadn't been for James Whale's classic movie (or brace of movies.) The Frankenstein franchise continues to run and run because the movie monster- as created by make-up artist Jack Pierce and actor Boris Karloff- is so compelling- at once terrifying and pathetic. Shelley's conception of the monster (a seven foot, murdering version of her husband) was very different and much less interesting.
We're studying Frankenstein for an Open University course. If I had had to choose a "Gothick" text for study I'd have settled on Beckford's Vathek- stylistically sure-footed and delightfully camp and decadent- or a set of stories by Poe.