trilogy?

Ok on the back of the omerta audio cassete box it says the final chapter in mario puzos landmark mafia trilogy. I know how last don and omerta are related, but the only other mafia books i can think of are the godfather and the sicilian, but theyre not really related to the other two so i dont see how either of those could be part of a trilogy. and fools die has some of the characters form last don but thats hardly a mafia book. so am i forgetting a novel or are they including the godfather? if they are it doesnt amke much sense.

What it means is that its last of the 3 books he wrote about the mafia. They arn't neccisarily related too much.

yes, the other one is The GOdfather