Mary was the daughter of a political philosopher, William Godwin, and famous feminist Mary Wollstonecraft, who died shortly after giving birth to her daughter. William Godwin provided Mary with a fairly thorough, though informal, education and encouraged her to follow his own liberal political theories.
In 1814, young Mary scandalously fell in love with the poet Percy Bysshe Shelley, who was already married at the time (his wife was pregnant, too. What a nice guy!). Nevertheless, he, Mary, and Mary’s stepsister Claire took off for France and spent a while kicking around before returning to England after Mary became pregnant. They struggled for a couple of years (society at the time did not take well to out-of-wedlock babies) but were finally able to marry in 1816, after Shelley’s first wife committed suicide.
Mary and Percy spent the summer of 1816 with Lord Byron, Claire (who was pregnant with Byron’s child), and John William Polidori in Geneva, where she conceived the idea for her most famous novel, Frankenstein. Legend has it, she came up with the plot of the book when she and the others were playing a game to see who could come up with the best horror tale to pass the time during the rainy, miserable summer. Frankenstein was published anonymously in London in 1818 and was published in France, under her name, in 1823.
In 1822, Percy Shelley drowned while out boating off the Italian coast, leaving Mary a widow with a young child. She returned to England and dedicated herself to writing and raising her son. She was plagued by illness late in her life and died in 1851 of a brain tumor, aged 53. Aside from Frankenstein, Mary was responsible for editing a number of her husband’s works; she also published five other novels, a travel book, and biographical articles for an encyclopedia.