Shelley has cleverly woven each of these reading together with evidence backing each of them and showing everything she dislikes as being monstrous. Thus we are able to model our opinion of monstrosity from her clever interweaving of different possible readings of the text. .
Mary Shelley, throughout Frankenstein uses many pathetic fallacies. The most obvious is when Frankenstein is just about to give the creature life "It was a dreary night of November- This word choice is what makes the reader start to doubt what Frankenstein is doing. Thus we start to wonder who is monstrous and question our original opinions. Mary Shelley also uses her word choice to her advantage in shaping our viewpoints (e.g "Great God! If for one instant I had thought what might be the hellish intention of my fiendish adversary, I would rather have banished myself for ever from my native country- - this showing how Shelley loathed Frankenstein's ambition but also showing a repentant side of Frankenstein that we didn't see earlier in the text). Shelley uses a structure she has created where there are three main points of view (Creature, Walton, Frankenstein) by giving both positive and negatives. With the style of writing from her time she is subliminally putting many hints to her opinion into the text, however still putting different points of view (e.g the creature is given many pages in the book to show his point of view, when if Shelley had wanted us to follow Frankenstein's point of view she could have just glossed over the creature's) in the piece so we are able to make up our own opinion and not be forced into hers. Thus giving us many options to model our ideas on monstrosity.
The fact that the novel is told in 1st person rather than 3rd person makes the reader question: are the views being expressed the ones that the author has, or the ones she wants us to have. We have 3 viewpoints in the text that we can choose to either disregard or follow.
