For most of the book, it is written in third person limited-focusing on Montag's own views, action, and perceptions. If it were universal-we would know all, not just the way in which Montag interprets things.
Third person limited is that in which we are not given all perspectives and do not have all the facts, only a character's interpretation of the events. Omniscient would bring the reader all the facts that are not known to the other characters.
Yet, there are times when descriptions of character conversation and detailed setting descriptions are used to move the plot along and give the reader another viewpoint.