A work of literature is very much a "personal" item and for one to understand it, one needs to understand the style and viewpoint of the writer. Style will determine style factors such writer's diction, punctuation, structure and characterization. If a reader is not accustomed to the level and manner in which all these have been presented, it will impact negatively on understanding.
A writer's point of view can pose as a problem if a reader sees things differently. If the writer takes a blatantly biased stance, it will lead to omission of other crucial arguements that a reader needs to make an informed judgement and ultimatley an informed understanding of the text.