Anna Karenina is a problematic story in that there are no sympathetic characters. All of the characters are sleazy at best, and revolting at worst. I had to be dragged into seeing yet another adaptation. The film opens by peeling back the fourth wall and engaging the actors entering their stage roles. I thought this was interesting, and then it became a theme in the film. Each scene the transition includes the actors leaving the stage and reentering new scenery. This was cleaver at first but quickly began stepping on its own feet as the self-reflexivity seemed to have no point other than to be clever.
Karenina herself goes though so many personal changes, it's not possible to bring it off believably in a two hour movie. At some point her flip-flops just come off as a crazy person and not someone I really care about. Keira Knightly is not a strong enough actress to pull it off. Some of the other roles fare better, particularly Jude Law as her husband.
I like movie adaptations that take chances; Ian McKellan's Richard III and Julie Taymor's Titus come to mind, but this film never rises above its source material. Tom Stoppard's screenplay is like reading the Cliff notes to the novel, there is no real substance to it.