The Killer Sex Game (Frank Boff) by Nathan Gottlieb

Frank Boff returns, taking on another righteous case. Boxer Danny Cullen, Frank's sidekick / friend, gets involved with the murder on another boxer, prompting Boff to investigate. He's still not fond of taking cases that involve getting people behind bars instead of away from them, but his wife insists, hoping it will mean he will go to heaven.
The case gets Boff involved with high class call girls and a dangerous mobster. The personal danger to Cullen and Boff is even higher than in the first novels, prompting Boff to come up with a pretty devious scheme that will show you why Boff is as much anti-hero as he is a hero. Written in Gottlieb's usual, easy to read and witty prose this is another great thrillride with some very funny but also very devious characters.