I personally fully agree! But I imagine a PM at Amazon was presented with the question "Should ratings of all versions of books be merged?". Unless they reall

I personally fully agree! But I imagine a PM at Amazon was presented with the question "Should ratings of all versions of books be merged?". Unless they really really cared (or personally had experienced dramatic differences between versions of books before), they probably said "Yeah sure". (I'm also biased a bit in that I assume that implementing this more fine-grained would cost more than $0).