Author Ian Wishart's second book on the Scott Watson case will be published next week.
Mr Wishart claims Elementary 2.0: The Unreleased Police Evidence on the Scott Watson Case will outline five key reasons why Watson is guilty of killing Ben Smart and Olivia Hope. The friends disappeared after boarding a mystery yacht moored in the Marlborough Sounds in the early hours of New Year's Day 1998.
Watson was convicted on their murders the following year and remains behind bars, although he has steadfastly maintained his innocence.
The book follows the January publication of Elementary. Its sequel will see the release of hundreds of pages of police evidence, and these put Watson "clearly in the frame" for the murders, Wishart said.
"It was always my intention to release the full police evidence of key witnesses.
"But the statements had to be vetted first to comply with legal requirements. Elementary 2.0 adds to what people have already learned from the first book, and makes key testimony available to readers on both sides of this controversial debate."
He expected less backlash this time, Mr Wishart said.
"They will actually be able to read key statements in full - and they've never had access to that before. This case has been based on two decades of incorrect information ... armed with the actual witness statements, people will be much better placed to debate the controversy."