hey, i had to say that The Godfather stood the test of time to become a great novel, also with the help of the popularity of the first 2 films.
Mario Puzo was def. a genius in writing. Sure he might not have written out scenes like Tom Clancey would, but his writing provides a calming feel, but with the subtle tension building around you as the plot thickens, ie Michael and Sollozzo.
His other book The Last Don, in some ways it was like a remake of the Godfather for television. I've never read or seen The Last Don, but my father has read it,a nd he tells me that it is on par with the writings of The Godfather. I would also like to see The Last Don II.