Red Diamond, Private Eye by Mark Schorr

A New York cab driver hacks around the city all day, but goes home to a collection of pulp fiction. His favorite character is Red Diamond, the ex-cop turned private eye who always has a gun at his side and a blonde named Fifi. One afternoon he comes home to find his wife has hocked his entire collection. This sends him over the edge into a new identity, Red Diamond, P.I. Now he's out in the city learning some deadly lessons.