Fatal Sisters (Rafferty) by W. Glenn Duncan

Patty Akister's husband goes missing. According to her he's a secret agent. Rafferty, who is hired to find him finds that pretty hard to swallow. When her husband turns up dead in a whorehouse Rafferty tries to find his killer while he goes out of his way to prevent shattering Patty's positive view of her husband.

This one has all the hallmarks of a good Rafferty tale. That is, nice banter between him and his girlfriend, macho and witty exchanges between him and his cool sidekick Cowboy for one. Aside from that there's some nice moral choices to deal with and some good action scenes.
As ever the writing is fast-paced and loose, making this a quick and easy read.