Frankenstein conforms to the gothic style in terms of plot, theme and language style.
The Gothic novel tradition, which began with Horace Walpole's The Castle of Otranto (1764), typically features dark and often supernatural events and brooding villains. These characters are cut off from the ordinary run of society by their sinful passions and deeds which exceed normal human limits and morals.
Frankenstein displays a pre-occupation with sin and evil and a premise which, although given some scientific trimmings, remains esentially a supernatural, or unnatural event. The awfulness of Frankenstein's passion and ambition in creating the monster is frequently emphasised:
Who shall conceive the horrors of my secret toil, as I dabbled among the unhallowed damps of the grave, or tortured the living animal to animate the lifeless clay? (chapter 4)
In this quote, Frankenstein appears not like a modern scientist but rather as some dark magician of the 'unhallowed' arts, dabbling in forbidden secrets of live and death, sinning against the natural order with his unholy experiments.
The kind of heightened, melodramatic language in the above quote, emphasising the more sinister side of human nature, is designed to work upon the emotions and create a suitable sense of fear and awe. This language style was common to the Gothic tradition, aiming as it did to depict characters and events far outside the normal, everyday level of things. Frankenstein is very much in the mould of the Gothic novel.