Originally posted by Cristina's Way:
I do believe that the Michael in the novel is a rather one-dimensional character whom Coppola made more complex on the screen (in GF1 and GF2, that is). That is why I don't think the "book Michael" is a good source for how the "film Michael" felt about Kay, how he felt about love, or how he felt about sex. (If it were, then Coppola would have kept all those details about him in the film; but instead, he changed them.)
That's funny - I mean, how opinions may differ.

To explain you my position only (God forbid, not trying to convince anyone

) - I am absolutely positive that the book is the only
original and the most integral part of the Godfather story, and the only possible source of knowledge on its characters. Most of the changes Coppola made to the book are untrue to characters, and the complexity and depth of Michael's character in the book is absolutely lost in the movie due to these changes. And not only Michael's. Book forever
