What is Winston feeling upon meeting O'Brien in the corridor and his offering of the dictionary?
Winston has developed a strange feeling of trust for O'Brien, who he suspects might even be a member of the Brotherhood and thus opposed to Big Brother. O'Brien confirms this in Winston's mind through an oblique reference to Syme, who has become an unperson. He takes this as a signal that he is to be trusted, and when O'Brien gives him his address, so that he might get an advance copy of the newest edition of the Newspeak dictionary, he believes that O'Brien is really saying "If you ever want to see me, this is where I can be found." He believes O'Brien is sympathetic to him, but also recognizes on another level that he has absolutely no rational or factual basis for thinking this. On the one hand, he is desperate to reach out to what he believes is a kindred spirit. On another level, however, he recognizes that this will like spell his destruction:
Even while he was speaking to O’Brien, when the meaning of the words had sunk in, a chilly shuddering feeling had taken possession of his body. He had the sensation of stepping into the dampness of a grave, and it was not much better because he had always known that the grave was there and waiting for him.
His encounter with O'Brien reveals a depressing example of "doublethink." He experiences a visceral feeling of hope and excitement, feeling that he has taken the next step from thoughtcrime. He has gone from feeling hate for Big Brother to writing it to what he thinks is active resistance. "The last step," he realizes, "was something that would happen in the Ministry of Love."