In '1984', why did O'Brien give Winston ^the book^?

[mediumdeadwood]

I'm currently reading it again and just got to the bit where O'Brien's given the book. I've never understood why he would do that, though.

Am I missing something?

...Probably

I don't remember it being properly explained. I thought it could be that O'Brien intended to trap Winston. It could also be that O'Brien is very good at Doublethink, being able to believe two opposing viewpoints at the same time.