I agree. To me Summer's Gone is the story of a troubled and tortured soul struggling to salvage and rebuild a life broken by tragedy. Not just in the case of the main protagonist but in the lives of other characters in the drama too. Bella is trying to gain acceptance and overcome some immense personal catestrophe, which befell her, which blighted and cast a shadow over her life and Victoria is living, without a hint of bitterness or self-pity, as a person disabled by a twist of fate, mustering the strength and determination, on a daily basis, not to passively accept her fate and give up on life but to fight like a tigress to rehabilitate herself, hoping against hope, to walk again unaided. All of the actors in Summer's Gone are like that to a greater or a lesser extent, having their own pasts, histories and stories most of which must inevitably have episodes of loss, tragedy, failure, rejection, difficulty, distress and sadness significant enough to affect their presents.
To me Summer's Gone is a tragedy about growth, redemption and salvation.
(None of which come, if they ever come at all, without struggle, heartache, sacrifice and pain.)
That said, to be honest, I think that it's likely that Summer's Gone will speak to each of us differently depending on who we are, what we have done, where we have been, who we have shared our lives with and what has happened to us personally. I believe that each of us may see and understand it differently if that makes any sense. As far as I am concerned Summer's Gone really is THAT deep. And it doesn't get much deeper than that, folks!