I started Tolstoy's masterpiece about three months ago, and just finished with it yesterday. I loved it, but it is a bit overwhelming. All of the characters get confusing, until you're about one hundred pages in. I do enjoy a good Russian family drama, though!
My one point of concern is the ending. Neither the "original" ending of Anna's train "misadventure" (don't want to ruin it for those who have not read the book) nor the musings of Levin really did it for me. I would say the ending is Anna Karenina's weakness. It actually makes me feel better about my writing that even a master like Tolstoy had trouble with his endings! And, actually that might be the greatest critique of all, and why his tomes are dangerously large.
Anna is so wonderfully characterized that I can see her, touch her, even smell her perfume as she wafts from room to room. The same with Vronsky, Oblonsky, Levin, Kitty, Dolly and the rest. I felt like I was a part of the family by the time I put the book down, satisfied but still in doubt. I wanted more.
Needless to say, the new film with Keira Knightly was not my cup of tea. I found it horrible and pretentious and should have left the theater when Tom Stoppard's name appeared as the screen writer. It was so self-conscious, and so British that I just couldn't stomach it. I don't even feel the movie deserves its own review, to be honest. Keira is too much of an acting lightweight to do justice to the role of ANNA but at least he costumes were fabulous!
If you really want to see a good screen version of Anna Karenina, I suggest the 1935 one with Greta Garbo. Now there is a femme fatale! Otherwise the 1948 Vivien Leigh version is also good, but a little melodramatic, as is par for the course with Leigh.