If you are referring to style I think you need to be aware of the context within which Hawthorne was writing and why he is referred to as a Dark Romantic. Dark Romantics, or anti-transcendentalists, were keen to point out the dark side of human nature, and the sin and inherent corruptibility within us all. This clearly ties in to the theme of this short story with its emphasis on hidden sin. What is key to the style of Hawthorne, therefore, is his ability to juxtapose natural description, with supernatural details or an emphasis on horror and fear. Consider the following passage:

Mr. Hooper raised a glass of wine to his lips, wishing happiness to the new-married couple, in a strain of mild pleasantry that ought to have brightened the features of the guests, like a cheerful gleam from the hearth. At that instant, catching a glimpse of his figure in the looking glass, the black veil involved his own spirit in the horror with which it overwhelmed all others. His frame shuddered - his lips grew white - he spilt the untasted wine upon the carpet - and rushed forth into the darkness. For the Earth, too, had on her Black Veil.

Note here how an everyday, normal event, is suddenly changed into something much darker and much more sinister. The minister, just about to drink a toast to the happily married couple, happens to see himself reflected in the mirror, and is "overwhelmed" by horror. Note the description of what happens to him: his body "shuddered", his lips turn white and he rushes into the darkness, presumably finding consolation with something else that has a "Black Veil" on. The mystery and penetration into the human soul that such passages offer clearly identify the style of Hawthorne.