I was wondering if the stories in Puzo's novels were all supposed to exist in the same world. What I mean is, are the Corleone's in Vegas along with the Clericuzios. I had assumed all the stories took place in different "worlds" but I just started Omerta and the Corleone and Clericuzio familys are mentioned briefly. Can anyone help?

The Last Don, which has the Clericuzios has nothing to do with the Corleone crime family from the Godfather.

I always assumed The Last Don was set in the late 80s/early 90s, as opposed to the 40s, or 50s I can't remember, for the Godfather.

The connection is that Puzo, having made a zillion dollars from "The Godfather," established a genre of organized crime novels that he knew people would buy because of GF. But, other than "The Sicilian," there's no connection between GF and his other novels.

The Corleones you mentioned in Omerta were the Corleonese clan. These are a real mafia clan based in Sicilia and have nothing to do with Vito and co. I can't quite remember fully their involvment in Omerta though.