Heads You Lose — Brett Halliday

After hearing a murder over the phone, Mike Shayne searches for the killer

Woken by the telephone, Mike Shayne is disoriented. Though he has been alone since his wife was murdered, he has not gotten used to sleeping by himself. The voice on the other end of the telephone snaps him back into reality. It's his friend Clem Wilson, calling from a filling station outside of Miami, and there is terror in his voice. He has time for just a few words before Shayne hears the crack of broken glass and the thud of a falling body.
 
By the time he reaches the filling station, the police are already there and Wilson has two bullets in his chest -- and either of them would have been enough to kill him. Clem Wilson was mixed up in something he couldn't handle, and if Mike Shayne can't set aside his grief and unravel the mystery, his friend will not be the last to die.

Heads You Lose is the 8th book in the Mike Shayne Mysteries, but you may enjoy reading the series in any order.