Describe the author's style, and give an example that demonstrates the style.

This is an  epistolary novel, which means the story is
told in the form of letters.  An objective narrator, Walton, writes letters to his
sister Margaret and in these letters, he tells the story not only from Victor's
viewpoint but also from the monster's viewpoint as Walton speaks to both Victor and the
monster at various times. Walton also inserts his omniscient point of view, so we have
three viewpoints in the novel - protagonist, antagonist and omniscient
narrator.

You can read more about the Romantic and Gothic
elements in the novel at the link below. There is also an interesting discussion of
the  Doppelganger effect.

The writing
style of this novel is even more archaic and cumbersome when the monster is speaking.
This is because when the monster was created, Frankenstein fled and did not think about
raising his "baby." So, the monster had to learn to speak and read on his own, while he
was in the forest. Plus, the first language he learned was French, not English. This
makes his speech very formal and archaic because he was reading works like
Paradise Lost in English. For example, after the monster kills
Victor, he says:

What does it avail that I now ask
thee to pardon me? I, who irretrievably destroyed thee by destroying all thou lovedst.
Alas! He is cold, he cannot answer me.