Since several people have brought up Gothic (only Ken Russell could render Gabriel Byrne and Julian Sands hideous), I will mention a much better (IMO) version of the same story, Haunted Summer. When I first saw it, I had low expectations because Golan and Globus had bankrolled it, but looking back I think it must have been their attempt to move into Merchant-Ivory territory -- not entirely successful, of course. Philip Anglim (who played John Merrick without make-up in a 1982 PBS production of The Elephant Man, or more recently had a recurring role as Vedik Bareil on Deep Space 9) makes a superb Byron, far better than Byrne's. Eric Stoltz is a winsome Shelley. Laura Dern is appropriately over-the-top as Claire. But the best part of the film is Alice Krige's (yes, the Borg Queen from the last Star Trek film) Mary. She is the focus of the film, which casts her as a worthy foil, if not quite an adversary, for Byron. Alex Winter (the non-Keanu from the Bill & Ted movies) plays Polidori as a pathetic hanger-on.
There are liberties taken with the story, of course, but not as many as you might expect. The landscape is lovely and beautifully filmed in such a way as to suggest paintings (the film opens with paintings, in fact). The scene in which Byron and Shelley compose verse off the top of their heads while sailing is especially well done. (I am no doubt biased because it shows Shelley to be the superior poet.)
I suppose the best aspect of this film for me, however, is how appropriately young the actors look. I have shown Haunted Summer to my classes, and always the students are shocked to see that these long-canonical figures were barely older than themselves. They may know it from their assignments, but to see it is a different matter. It casts their experimentation, sexual and chemical (yes, the first opium-smoking scene invariably draws a few chuckles from undergraduates) in a very different light from Gothic, which makes them out to be decadent and haggard. I have found students' interest usually piqued by Haunted Summer, whereas most are simply repulsed by Gothic. Incidentally, Haunted Summer also makes use of the Fuseli painting Rick Albright mentioned. I understand Haunted Summer is based on a novel by Anne Edwards using Mary Shelley's journals.
Richard A. Nanian
Romantic Circles / Scholarly Resources / Fictional Representations of Romantics and Romanticism / Review of Haunted Summer