I'd like to comment on the earlier post about how FFC changed Fredo's character. I humbly disagree. In the movie, he is being sent to Vegas to learn the casino business. In the novel, he's sent out there because he has basically had a complete mental breakdown after witnessing his father's shooting. Once there, he not only recovers, but becomes a real ladies man and very sexually active, something that would displease his father. That may very well start the seeds of resentment in Fredo, that he was in his father's bad graces while Michael is the favored son and inheriting the whole business. Eventually, that resentment would build (slutty, drunken Deanna vs. Kay and her classy friends), as the differences in their lives becomes more apparent to Fredo. Although Michael's life was very far from perfect, Fredo thought it was.