I think it helps to set the scene that this novel is going to operate as a critique of both Romantic and Enlightenment ideas. Shelley is very conscious of both, with a father representing the latter and a husband representing the former. Both forces presented diametrically opposed views of how to appropriate reality, the nature of consciousness, and how the external should be perceived. It is within this paradigm that Shelley operates on critiquing both ends as means to appropriate reality. At the same time, the notions of construction and creation are brought out in the introduction, suggesting that the implications attached to both apply to she and to Victor. The introduction helps the reader understand that there will be an intense amount of intellectual and moral implications and complexities presented. It helps to set the stage for that exploration.
It also tells us how she came to write it. It began as a sort of exercise to pass some time, a challenge to write a horror story when she was visiting with some friends in Geneva and the weather was cold and rainy. She also says that the subject was of interest to her because she was interested in the ideas of Darwin. She states that in presenting a scientifically impossible situation, she was able to explore the depths of human passions in a way that she might not have been able to under ordinary circumstances. Nevertheless, she has preserved what she believes are the “truths” in human nature, even though dealing with the bizarre and fantastic. She also denies that she had any purpose in espousing any doctrinal position (“nor is any inference justly to be drawn from the following pages as prejudicing any philosophical doctrine of whatever kind”). She also said that she was going to write other tales, but the weather cleared up, and that was the end of it.
Do you believe what she says? There is so much depth in this story and the themes are so profound, it is hard to believe it is only a lark. However, that may be attributed to the genius of Mary Shelley. She was only 19 when she wrote this. Amazing.