1984 Section Two, Part IX Analysis (pp. 179-218)
This section consists almost entirely of long passages from Goldstein's book. The book provides the reader with insight to how the Party seized and is able to maintain control. The statements in the book are probably true in the world of Orwell's novel, however, the reader will later learn O'Brien helped to write the book. Because the book is written and distributed by the Party itself, the statements within could well be lies (though the explanations of the Party's motives and strategies are so apt as to lower the probability they are lies.) The book is characteristic of Orwell's irony throughout this work—it is a fake book (that is, it's not actually written by Goldstein for the purpose of overthrowing the Party) that contains true information, or at least information that is most likely true.
Another possibility, though unlikely, is that O'Brien did write the book with the goal of revolution in mind. In later chapters, O'Brien says he came under the influence of the Party a long time ago. It is possible then O'Brien wrote the book with the intent of overthrowing the Party, but was then captured and converted in a manner similar to Winston. However, O'Brien is not as broken as Winston is by the end of the novel, and he has escaped execution, which no other traitors have, making this reading unlikely.
Two minor literary devices worth noting in this section are foreshadowing and word choice. While discussing modern science, the book details the process of torture practiced on prisoners. The description also serves to foreshadow what will happen to Winston in the Ministry of Love. Orwell uses a great deal of sexual imagery/words to describe both the rented room and war in general.