It had its moments, but...
I say this as a fan of so-called 'period dramas'; Mary Shelley was... well... boring. The entire cast seemed really wooden and even their attempts at depicting what must have been a great deal of passion, discussion, partying, and debauchery seemed forced. The lives these people led remain the stuff of fascination and debate even now, 200 years later. You would think then that the film would have even the slightest interest in telling that story. We don't even meet Byron until halfway into the film. The moment that the story competition is conceived is glossed over, as is the penning of Frankenstein itself.
I don't know. I'm not exactly a critic, but I feel disappointed. I expected this film would be somewhat more grand and interesting. Instead, we're left with something that pretends to be a love story, but never really gets around to telling it. Some of the 'facts' are also incorrect or misleading, and some of the most scandalous parts were omitted for reasons I don't understand.
It's like a really boring professor gave a lecture that made me fall asleep. The material had a lot of promise, but the movie falls flat.