The Game of Thirty, by William Kotzwinkle

A hard-boiled PI takes on a murder case the police haven't been able to resolve for the victim's daughter. Her dad was killed, and then eviscerated, in his living room. He was a dealer in ancient artifacts, as is his daughter, and was involved in some shady trades one of which involves child prostitution. However, the main story was a little too obvious to me. Still, very interesting. The game of thirty interests me. And the ending was rather fairy-tale happy, in a good way.