I was blown away by Anna Karenina. I've been reading it for a long time; I got very distracted from it for a few weeks. But Tolstoy's writing is just amazing, the psychological realism was so intense at times, and the richness of all the different characters. I was most caught up in the story of Anna and her lover, and the demise of that affair. I was pierced by their miserable relationship, described so, so vividly. At times I was equally drawn to Levin's story, which was really the more important story. But there were so many long descriptions of various political issues and details about farming that I found myself impatiently skimming chunks. His internal struggle, however, the intense scenes at his brother's death and his son's birth, moved and gripped me. I was also deeply moved by Karenin, another vividly drawn and realized character.
As I said, the death and birth scenes were particularly intense. I was also kind of shook up by Levin's final existential crisis, and even slightly, if wistfully, convinced by its resolution.