If you've ever read a book about the murders of Olivia Hope and Ben Smart, you'll need to read Elementary, too.
In fact, it will help immensely if you've read other books about the murders. Ian Wishart's second run at the Marlborough Sounds' murders of New Year's Day 1998 is not a great literary effort.
It is, though, a detailed account of the evidence police used - and more importantly did not use - to convict Scott Watson. The evidence includes chunks of material that has never been made public, and Wishart has used it to build his own case against the convicted murderer, currently serving his 17th year in prison.
The book does three things. First, it gives people a different picture of Watson. Much of what has been written in the past 15 years has raised questions about the police case, but has had the byproduct of softening Watson's image from convicted murderer to someone potentially mistakenly jailed.
Elementary "doesn't pull any punches", Olivia's father, Gerald Hope, told me yesterday. He's right. Wishart has included a large number of unsubstantiated statements made to the police during the inquiry - claims that have never been tested at trial.
What emerges is the portrait of someone who is very different from the "airbrushed" public image, as Wishart calls it.