The other key part of the book, for me, at least, was the use of the paintings of Hieronymus Bosch. Harry's real name is Hieronymus Bosch. He is named for the 15th Century painter whose work is replete with depictions of the wages of sin.

When I first created Harry Bosch and gave him the painter's name, I did it with the idea that the name was metaphor. Bosch the painter created strange landscapes where good and bad actions are played out in chaotic scenes. Five centuries later Bosch the detective moves across a chaotic city where good and bad actions are played out before his - and therefore, the readers' - eyes. I wanted with this book to explore this correlation and therefore I made the paintings a pivotal part of the story.

A strange coincidence occurred to me while I was researching this part of the book. I was very familiar with the works of the painter Hieronymus Bosch. I had a collection of books featuring his works and writings about him. I had written several of my Harry Bosch novels in an office where prints of the paintings hung as well.

But I was unfamiliar with the workings of an art museum, which would be important to describe in the novel.

A friend set me up with a curator at the newly built Getty Museum in Los Angeles. Sitting atop a mountain like a foreboding post-modern castle, the museum itself was a perfect location to use in a crime novel. I told the curator my plan for the book was to have my character McCaleb come to the museum seeking an expert on the paintings of Hieronymus Bosch. He would then be shown a Bosch painting and the fictional art expert would comment that the night sky in the painting showed "a darkness more than night," thereby giving the title of the book life and metaphor all at once.

The catch was I knew that the Getty did not have a Bosch painting in its collection and that I would be creating fiction about a real Los Angeles place. Not to worry, the curator told me.

He escorted me to the Getty's restoration laboratory where coincidentally a Bosch expert was restoring a Bosch painting sent to the Getty from a museum in Brazil. I watched the restoration process for a long time and in the night sky of the painting I saw a darkness that was certainly more than night.

It was a strange coincidence, a case of art imitating life imitating art. Or vice versa.

I think that what is also explored in the book is the difference in styles between Bosch and McCaleb. I wanted to show how clearly different these two men are.

Both are very good investigators and both are bonded by an earlier case that is referenced in the book. But they operate on different levels of motivation. They are not fueled by the same pump.

Bosch has deep emotional conflicts from which he draws his fire. In a way, he is making up for wrongs done to him when he rights wrongs as a homicide detective. In a way, he is an avenging angel, as McCaleb himself notes in the book.

But McCaleb is different. He is less instinctual and more intellectual about putting the puzzles of crimes together. He is not an avenger. I think he is some one who is motivated by common decency and a desire to see that no bad deed go unpunished.

He carries inside a transplanted heart, and with it the knowledge that someone had to die in order for him to live. It has given him a view of the world, and his place in it, unique from Bosch.

I think putting these two different men and different views of the world and different styles together makes for interesting conflict and story. This was not to be a "Butch and Sundance" story.

I felt certain as I wrote this book that these two men could not share the same pages easily, that when Terry McCaleb looked into the darkness of Harry Bosch's eyes that he would see something that haunted him. Perhaps, the cost of looking so long into the abyss.