The novel, while crudely written compared with the polish of the film, did have many interesting and useful details and side stories that didn't appear in the film. The best were: the Bocchicchio Family and how they helped Michael return from Sicily; Neri's background and recruitment; Sonny and the boiler inspectors; Vito's war with Maranzano. I could have done without all that Lucy/Jules crap (a flimsy vehicle for Puzo to describe her gynecological operation); all of Nino, and nearly all of Johnny following Connie's wedding. Most of that was Puzo's way of showing off what he learned about Hollywood. That Hollywood BS ruined "The Last Don."
While I agree with most of your list, I thought the description of Vito's war with the Maranzano was laughable. Coupled with Vito's letter to Al Capone made up a considerable weakness of the novel. I always hate when writers do things that are so transparently obvious.
I like the extra features the novel has as Turnbull described as well. But the novel also has so much fluff (the entire Johnny Fontaine storyline and being a main character, the storyline of Jules and Lucy) that it detracts from the parts we have been accustomed to from the film.
As others have stated previously, I think Puzo was trying to show the reader how much he "knew" that some of it came at the expense of the story (the "Hollywood" thing, the anatomy of a woman, etc
).
