Who wrote the original Frankenstein?

Who wrote the original Frankenstein?

Mary Shelley created a monster out of her "waking dream" – but was it her husband Percy who "embodied its ideas and sentiments"?

Frankenstein – that most resonant and enduring of early nineteenth-century fictions – was born in the febrile atmosphere of the Villa Diodati in the summer of 1816. Bored by the unseasonably cold, wet weather, the Villa’s residents, Byron, John Polidori, Percy Shelley and the eighteen-year-old Mary Godwin, amused themselves by writing ghost stories.
http://entertainment.timesonline.co.uk/tol/arts_and_entertainment/the_tls/article5035717.ece