Early reviews:

Falco’s depiction of Vito Corleone captures both the cool reserve of young Vito and the insight he demonstrates as Don. A worthy addition to the lurid world of the Five Families.
–– Kirkus

“…channels the original so well that readers will be vividly reminded of Puzo’s strengths . . . His moments of blam-blam-blam are ace. Best of all, he supplies a grand set-piece finale--a parade-that will leave readers dreaming of just one more movie.
–– Booklist

Falco’s solid Godfather prequel fills in the backstory of the iconic New York City Mafia family . . . Puzo fans will find this a refreshing change..."
–– Publisher’s Weekly

I can't help but think this may finally be a good addition to the original novel, and if true, could be considered canon. I suspect Paramount just want's a cut of the action. I would be suprised if the novel won't see the light of day.