I would include the horrific, secretive story about Luca that the Corleones didn't even want Mike to know about( you know the one I mean!). I'd rather them show it just as the book depicts rather than just having Tommasino and the old doctor telling Mike about it. Graphic? Yes. Horrible? Absolutely. But it paints Brasi more fearsome and brutal, something which I think was lost in the switch to cinema. To non-novel fans, Luca is like a big, dumb teddy bear, and they're not surprised when he gets himself in trouble at Tattagila's bar. (Furthermore, I might include his hunting down those 5 or 6 guys who tried to take out Vito 10 years earlier.)