Valachi laid the groundwork and was more important in understanding Cosa Nostra Rudy did say Joe's book helped him in building the Commission case. But it didnt play a big role in other cases or trials.
The main value of Bonanno's book to Giuliani was that he found in Don Peppino's description of the Commission a model of a "Racketeer Influenced Corrupt Organization" that the RICO law could be used against. RICO had been on the books since 1970, but Federal prosecutors were reluctant to apply it because they didn't know how to build a case. Giuliani recruited G. Robert Blakey, the author of the RICO Act, to sit with him and his team and coach them on how to use the law (Giuliani referred to Blakey as "my consigliere"). Blakey had impressive credentials: For decades he'd been an investigator, then chief counsel, to the Senate Permanent Investigations subcommittee, then chief counsel to the House Select Committee on Assassinations.
The main value of Valachi's televised testimony, IMO, was twofold: First, millions of Americans who weren't New Yorkers or Chicagoans learned that there was such a thing as a "National Syndicate of Organized Crime." They may have been aware of "gangs," or "Italian mobs," or "The Black Hand" from movies, but Valachi's testimony gave OC a national perspective. Second, it lit a fire under the FBI, which had previously largely ignored LCN.