Question

Read the passage. The Publishers of the Standard Novels, in selecting Frankenstein for one of their series, expressed a wish that I should furnish them with some account of the origin of the story. … I shall thus give a general answer to the question, so very frequently asked me: “How I, then a young girl, came to think of, and to dilate upon, so very hideous an idea?” What is Mary Shelley’s purpose for writing the introduction to Frankenstein?

Answer 1

I think it is because she had a hard time of it with Percy Bysshe when they were in Italy and wrote Frankenstein to "get back at him" once they returned to the UK. Although she had also a competition with her friend in which who has the best ghost story.

Answer 2

to give due credit to Lord Byron and others who inspired her novel