This is a good, shortened version of the six or so volumes of FBI electronic surveillance of Sam DeCalvacante. The author does a good job at providing context for the excerpts. He adds very little interpretation, leaving it up for the reader.
The coverage of topics is also excellent. Most of the conversations were within the New Jersey Mafia Family. The author show how the family operated, and the responsibilities expected of different-ranking members within the family. The excerpts also show how the small family interacted with other Mafia families.
The parts about DeCalvacante acting as mediator in the Bananna Mafia War are also enlightening. They provide a different picture of the conflict than that provided by Joe and Bill Bonanno.