There are many ways to answer this question. One way of looking at 1984 is as a political satire. Orwell was clearly satarizing the policies of Stalin in Russia. 1984 falls into the dystopian genre. It is similiar to Brave New World in showing a depersonalized society. This is the opposite of Utopian literature which has its genesis in Thomas More's text Utopia.
It depends on what type of style you are talking about. Orwell writes in third person, but the story is point of view from the perspective of Winston Smith. If you are referng to the language of the book, then Orwell creates a whole new language "newspeak" to show the power of language. Words are strong, and to strip them of their meaning the totalitarian government has to change them. The structure of the novel is three parts plus an appendix. There is more on the style of the novel here:http://www.enotes.com/1984/26922