I enjoyed (possibly the wrong word) the book, but agree it is a huge caricature.
It's almost a bit lazy in places... Franklin is clearly aware of the problems between Eva and Kevin but does absolutely fuck all about it?
Eva believes that her son caused significant damage to her daughter and other than wringing her hands does pretty much fuck all about it? Apart from deciding not to let him babysit her anymore.
I don't think the aim of the book is a nature vs nurture argument - the events of the book are simply too unrealistic for any argument either way to hold much merit.
Given Shriver's own comments about it, I think it's a child free woman's treatise on what could go wrong if you have a child - either you have a born evil wee fucker who you cannot control or change, or you have an innocent new born who you fuck up inexorably - either way the end result is the same.
Clearly, Shriver has used extremes in this - both Kevin and Eva's behaviour deviates far from the norm.
The theme of Eva's loss of identity is recurrent throughout the book - from the guilt tripping regarding her business and overseas travel, Kevin's destruction of her study, the move to the suburbs to finally being forever famous not as a successful business woman or her personal achievements but because of her mass-murdering son.
Again, we are talking about extremes, but as a child free by choice woman myself, one of the factors that lead me to that decision was the prospect of losing 'who I was'.
sorry for the essay. I should be tidying so am procrastinating on mumsnet