Ubet the book is excellent, CC!
I think Al Pacino perfectly fits my mental picture of Michael Corleone from the novel. But I always pictured the Don as someone smaller, portlier, perhaps older than Marlon Brando (not that I had any problem with Brando as Don--far from it!). Also, the cover of the first paperback edition had a drawing of Don Corleone that looked nothing like Brando. I guess I would have pictured Danny Aiello, Marc Lawrence or Anthony Quinn as closer to my mental image of the Don as I gathered it from the novel.