Let us remember that often authors will change or alter their writing style during the course of the novel. They do not keep their writing style precisely the same. However, having said that, when we think of style, we focus on the choice of words or diction, amongst other things. Shelley often uses a combination of powerful words, especially to describe the thoughts, feelings, emotions and desires of Victor Frankenstein. Consider, for example, how he describes his fascination with learning in Chapter Two:
My temper was sometimes violent, and my passions vehement; but by some law in my temperatue they were turned, not towards childish pursuits, but to an eager desire to learn, and not to learn all things indiscriminately... It was the secrets of heaven and earth that I desired to learn; and whether it was the outward substance of things, or the inner spirit of nature and the mysterious soul of man that occupied me, still my inquiries were directed to the metaphysical, or, in its highest sense, the physical secrets of the world.
Let us consider Shelley's choice of langauge here. Grandiose phrases such as "the secrets of heaven and earth" point towards a powerful style, as do the use of words to describe the more violent and emotional side of Frankenstein. Consider how words such as "vehement" and "violent" were used in relation to his "temper" and "passions." Victor Frankenstein is a man of obsessive excess, and the style which Shelley gives him serves to underline this.