Not as interesting and substantial as it could have been.
My problems with "My Sister's Keeper" were with the characters but not the story. The story that centers around Anna (Abigail Breslin) being born to be a donor for her leukaemia-stricken sister and then seeking medical emancipation from her parents so they couldn't force her to continue to donate her organs - is actually a great story. I found it original and intriguing.
This film is also about characters and their relationships. They explored the mother-daughter relationship between Sara (Cameron Diaz) and Kate (Sofia Vassilieva) and between Sara and Anna. But in doing so, they broke some fundamental rules of screen writing. To advance the plot, Sara acted out of character, and so did Anna. These characters were so inconsistent that any attempt at exploring them was pointless. The other relationship angles that they started, between husband and wife and son to the rest of the family, were conspicuously dropped, probably because they wouldn't be able to keep them in character either.
It was an odd mix of strong actors and weak characters. The lesser-known actors, Sofia Vassilieva, Jason Patric and Evan Ellingson were much stronger and were able to keep the light on their quieter characters. Vassilieva, in particular, stole the movie. Cameron Diaz played the mother, who was of course supposed to be unlikable. The problem is that ever since "The Mask" (1994), Diaz has been desperately trying to prove that she isn't just beautiful and she can play the unpopular characters too. Cameron is a good actress and she has long proved her point. The character of Sara would have been much better served if she was played by a not-so-desperate actress. And I think I have had my fill of Abigail Breslin.
The poor writing really detracts from the enjoyment of this film. I would be surprised if the book was this poorly written, but I'm not sure I care to find out. "My Sister's Keeper" could be a very interesting and substantial film, if written with quality. Unfortunately, this version is not.