Lenny Parker stories. This one is perhaps a bit more action/adventure than straight PI, but a nice read nonetheless.
Ex-Army Ranger Steve Madison is now a troubleshooter in the music business. He's hired to help a blind music superstar get out of some nasty business with a bunch of drugrunners. What follows is a story that could have been a Don Pendleton Executioner story with a lot of violence and an almost superheroic protagonist. Definitely the book for fans of classic Men's Adventure paperbacks, not if you're into Sue Grafton.
There's also three short stories two of which featuring Steve Madison that are nice fast reads included.