The thing with Marcello is that he was and still is low key to every one interested in crime, past & present.
He wasn't American or Italian, he was born in North Africa. He didn't run the big families in the large cities, his domain was the South. If I remember correctly I'm sure he was based in New Orleans. I would put him as about the same ilk as Santo Trafficante.
I know that he had dealins with Costello, something to do with the wire service, that gave the racing results. He also was a 50-50 partner on slot machines, this enabled him to get an early foot in to LA and therefore Vegas. I'm also positive that he was a big importer of herion, although I could be corrected on this point.
Being based in the south, he did have an affection for Cuba, not just in the money sense as those families in New York. When Castro came to power, all the families lost money, albeit only after Castro seized their holdings, bank accounts and hotels/casinos. Originally they were to work together. However it seemed that he had a altogether more intense dislike for the new Cuba. This seems to fuel the constant rumour that he along with other head of families had a hand in the JFK shooting.

Little Man: Autobiography of Meyer Lansky, skims he dealings with Carlos.

Another good point is any James Elroy book, American Tabloid is a perfect example, although his style of writting can be annoying. Also he will mix truth and fiction, but he does give you a taste.