What is the author's style in The Valachi Papers by Peter Maas?

The book, "The Valachi Papers," is told in the third person narrative and is based almost exclusively on an insider's account of the operations of the shadowy crime organization known as Cosa Nostra. Joseph Valachi was a soldier in one of the five New York City Families of the Cosa Nostra. He saw first hand the operations, structure and brutality of this crime syndicate. As the Feds learned more and more information from him and were able to confirm much of it with intelligence they already possessed, they came to the conclusion that Valachi had outstanding retention and a remarkable recall of dates, names and places. No better authority could exist to provide the information that Valachi handed over to the Federal authorities.