Reading this I thought of Agatha Christie's Miss Marple. It is a good mystery (who-did-it) book, where the main character does not want a great deal of attention but rather to be allowed to investigate circumstances of a crime.
Imagine getting a letter in the mail, where the anonymous sender asks you to think of a number. After you thought of a number, the sender contacts you once more, and reveals exactly that number, that you thought off. Would that not be creepy? The retired police investigator, Dave Gurney, is contacted by the letter's reciepient (they know each other from colleague but lost contact) and asked to look at this matter as an consultant.
Page after page you are drawn deeper into the story with more details that you are unable to connect, and you have to read on to figure this out. So why the Miss Marple comparison? Well Gurney and Marple are both looking at actual facts and not some random whimsical facts - a great attention to details that needs some mindpuzzling, an art they are both excellent at.
John Verdon's book is simply one of those, that you do not want to put down until you have read the last page - the one recommending this book to me had warned me about that fact, and I am so glad that she lured me into reading this.