If the GF were based on actual characters, such as the untouchables, then I think it will be approiate use outside sources to check the validity of the godfather. However, with fiction we are seeing to visions of two different artist (puzo and ffc) of the same characters. Some events and characters do overlap. Most are changed, added in one media and omited in another.
Soon, we will be enjoying the newest version of the godfather in novel form. The novel will be based on the characters in the book not the movie.

Therefore, I respectively disagree. Its better to enjoy the two versions of the Godfather seprately because their are too many polar differences between the two.