Books that read you as you read them

Today in the US people read more digital books than the printed variety.
Soon your 'Kindle' will have face recognition and biometric sensors, 

it will know what made you smile and what brought a tear to your eye and what made you quietly fume.
And how will this happen? While you quickly forget what you have read, the device(s) face recognition and biometric sensors, overseeing your reading will, with uncanny precision, never forget your reaction to each sentence you have read.