Why did Mary Shelley write Frankenstein?

Mary Shelley grew up in a world of intellects and literary elites. It was only natural that she would follow suit. An avid reader, Shelley's love for novels like Paradise Lost would later reappear in her own text. Shelley's husband was a famous poet, her mother an author and leader in the feminist movement.

During an evening of intellectual discussion, the famous Lord Byron made a challenge to those present.... who could write the scariest story ever.... this was a direct response to the horrific storm outside and their time spent sharing ghost stories. Mary dreamt about her monster that night and took up Byron's challenge.

When I placed my head upon my pillow, I did not sleep, nor could I be said to think. . . . I saw__with shut eyes, but acute mental vision__I saw the pale student of unhallowed arts kneeling beside the thing he had put together. I saw the hideous phantasm of a man stretched out, and then, on the working of some powerful engine, show signs of life, and stir with an uneasy, half-vital motion. Frightful must it be; for supremely frightful would be the effect of any human endeavor to mock the stupendous Creator of the world.