I'm just curious if I was the only one who made the assumption, based on my understanding of Tolstoy, that he is comparing and contrasting male infidelity through the brother and female infidelity through the sister, and implying that female infidelity is unacceptable while male infidelity is tolerable. It is possible (though I personally think unlikely) that he was trying to compare and contrast purely physical dalliances with full-blown affairs, without reference to the sex of the adulterer. I just didn't take that away from the novel. It was more "Boys will be boys, but you women had better watch yourselves".

As for the opium part, I think that Tolstoy did a very good job of showing, without explicitly stating it, that the opium was making Anna more and more erratic.

I was also unclear whether Anna had simply had an abortion when she was sick that made her incapable of having more children or whether she had had a full hysterectomy. How did you read that point? The original text was censored at that spot and so it's hard to tell what exactly was meant.