Murder for Madame — Lawrence Lariar

When a Manhattan madame makes a date with death, a detective must expose the sordid secrets of her clientele.
 
Lawrence Lariar was one the most popular cartoonists of the twentieth century. But from the 1940s through the 1960s, he also crafted a line of lean and mean detective and mystery novels under his own name as well as the pseudonyms Michael Stark, Adam Knight, Michael Lawrence, and Marston La France. Lariar now gets his due as a leading artist in hardboiled crime fiction.
 
Courting café society, Mary Ray was the queen of New York's priciest escort service. Until private investigator Steve Conacher finds his old friend stabbed to death in her brownstone brothel. All eyes are on her hot-tempered lover, and when he commits suicide in his Greenwich Village studio, it seems the case is closed. But Conacher's not buying the guilt and grief bit. Not when Mary's revealing appointment book has conveniently disappeared.
 
Without it, getting a lead isn't going to be easy, but Conacher does have one beautiful hook: a peach named Joy. The former call girl still has the shakes. And secrets. All he has to do is find her. With Joy's help, Conacher will avenge Mary's death even if it kills him. Considering the high-class lowlives he's dealing with, it just might.
 
Murder for Madame is the 2nd book in the PI Steve Conacher Mysteries, but you may enjoy reading the series in any order.