What do you mean by canon?
A "canon" is an officially recognized body of work. For instance, "The works of Shakespeare are a part of the canon of Western literature."
As applied to the Godfather I do not believe anything other than the original novel and the three films form the "canon" of "The Godfather," and these Wiengartner books and other efforts to make a GF IV are not a part of the canon, and they are also an infamnia!
