This question refers to the book 1984, by George Orwell. The novel tells the story of a dystopian future in a superstate called Oceania. The citizens of Oceania are constantly lied to through propaganda, spied on by the government and have their thoughts restricted. However, the main character, Winston, secretly rebels against the party by starting a relationship with a fellow worker: Julia.
The struture of this book is well-defined. It is divided in three sections. The first section deals with the setting of the story, and the development of Winston against it. The second section tells us of Winston's transformation. He is able to gain temporary happiness with Julia, and his thoughts are increasingly rebellious. The last section is one of suffering and torture, as he deals with the consequences of his actions.
This structure would change if other characters were to tell their story. Julia did not have the same type of rebellious thoughts Winston had, so this transformation would be difficult to express. However, she had rebelled in small, different ways before, so her background story could be more important than that of Winston. On the other hand, O'Brien never experienced a break from party ideology. He believes it wholeheartedly. However, his past could give us an insight into how the party developed and rose to power. Therefore, it is likely that a story from his point of view would focus more on past events instead of recent transformations.