A writing style refers to how a writer chooses to write. A writer may choose to write with a technical, conversational, or elegiac style. Another way to look at a writer's style is to examine his or her use of rhetorical devices, sentence structure, word choice, and tone. Depending upon what the author wishes to portray to readers, writing styles will vary greatly.
Mary Shelley's writing style is very Romantic (as in the Romantic Movement). She tends to use elevated language (not conversational or informal at all), numerous literary (rhetorical) devices, and presents nature as possessing great power. She desires readers to use their imaginations (fueled by her desire to "contrive one [a monster] which would frighten my reader as I myself had been frightened that night!"--taken from Shelley's 1831 Preface), another Romantic ideology. In doing so, Shelley fails to "fill in the blanks" (provide all of the details) for the reader when it comes to Victor's creation. Shelly leaves much of the imagery up to the reader, only providing him or her with snippets for details.
Shelly's use of figurative language is beautifully woven throughout the novel. In chapter two, she provides a simile comparing Victor's passion to a mountain river: "that passion which afterward ruled my destiny I find it arise, like a mountain river." In chapter twenty four, Shelley uses metaphorical language to compare the monster to an abortion: "I, the miserable and abandoned, am an abortion." In chapter one, Shelley includes personification. When defining Beaufort's home, Shelley personifies misery and despair by giving them the ability to welcome Victor's father (Alphonse):"misery and despair alone welcomed him."