Have just read your critique, D.B.C.H., and I have to say I'm with you on every point.

When I first got Puzo's Godfather novel, I stayed in bed for three days reading it and wouldn't even answer the phone or the door. When I got MW's Godfather novel, it took me four months of vague perusal to reach the end. And it was only my desperate hunger for anything GF related that made me finish it.
I can't bear the fact that the films are finished, that Hagen's dead, that Mike's story is over... but I would happily endure that abyss rather than see somebody walk in and, as you so perfectly put it, bastardize a cast of characters that millions of us know so intimately and love so much.

In England, MW's book was released as "The Godfather - The Lost Years" which strikes me as a much more appropriate title for what MW was trying to do. But still, I don't feel that he in any way enlightened us about the lost years, about events we needed to know about in the fifties or stories we wanted to hear from the twenties. Kay's abortion revelation was not MW's to make. Francesca, Kathy and Billy - why? Why write any of that? And for me the most disturbing problem is that the delicate tragedy Puzo and Coppola created for Fredo (his inadequacy, his percieved unjust treatment, his fatal mistake) was according to GFR really to do with his feelings about his sexuality, and some out-of-the-blue cemetary scheme that MW obviously dreamt up.
There's a saying in writing that you're supposed to be able to 'kill your darlings' - that is, all your favourite phrases, sequences, ideas, events - you should be able to get rid of them if they're not entirely necessary to the art. And it just feels to me, reading GFR, that MW had a lot of darlings, and he didn't get rid of any of them, and the result is indulgence.
The only way I can reconcile myself to having read this book is by thinking "that would have been an interesting way for things to have turned out. Good job they didn't" and promptly telling myself that none of this has happened