The novel is rough-edged and often reads like a first draft, vs. the brilliant polish and attention to detail of the film. But, Puzo was a great storyteller, and the novel has many side stories that add rich detail and understanding to the Corleone saga. Among the best: The Bocchicchio's and how they helped in Michael's return to Sicily; Neri's background and recruitment by Michael; Sonny and the boiler inspectors; Vito's rise; Luca's background.

Alas, Puzo was one of those writers who couldn't resist loading GF (and especially, "The Last Don") with endless, irrelevant detail about stuff he experienced in his life. He spent a lot of time in Hollywood. Johnny Fontaine, who served a useful purpose early in showing us Vito's generosity and the reach of his power, later becomes an endlessly boring vehicle for movie industry insider detail (which was the ruination of "The Last Don"). Same with Nino, who's even more irrelevant to the main story. Also, some female friend or relative of Puzo's had a gynecological operation that intrigued him. So, he loaded us up with all that Lucy/Jules BS just so he could describe the operation that he learned about.