Those conversations didn’t produce any significant revelations. But they do give insight into Mr. Trudeau’s perspective on several issues, including his working relationship with Jody Wilson-Raybould during her time as a cabinet minister before the SNC-Lavalin affair. Earlier this year Ms. Wilson-Raybould accused Mr. Trudeau and his aides of exerting undue pressure on her to settle a corruption case against SNC-Lavalin, an engineering company, with a large fine, not a criminal conviction. Mr. Trudeau said he feared job losses from a criminal conviction, with its accompanying ban on government contracts.

But the account of SNC-Lavalin and Ms. Wilson-Raybould is also a major problem for Mr. Wherry’s book. Because of publishing schedules, Mr. Wherry and Mr. Ivison were wrapping up their manuscripts about the time the SNC-Lavalin dispute came to the public attention in February. Mr. Ivison dealt with it by adding an extra chapter near the end, which is one of his book’s weaker sections.

But Mr. Wherry was able to discuss the situation at some length with Mr. Trudeau, Ms. Wilson-Raybould and others. He had so much access, in fact, that this week Lisa Raitt, the Conservative deputy minister, unsuccessfully called for Mr. Wherry to bring his interview transcripts to the House of Commons ethics committee so that it could determine if the conversations broke cabinet secrecy rules.