Highly recommend these books:
Wm. Kent Kreuger (Cork O'Connor series), C.J. Box (Joe Pickett series), Nelson DeMille John Corey series), Martin Cruz Smith (Arkady Renko series), Julie Kramer, Patricia Cornwell (Kay Scarpetta series), John Sanford (Virgil Flowers series)
They are not about Privet Investigators exactly, they are about reporters, rangers, game wardens,police officers, medical examiners, ect. They are all trying to solve murders and or mysteries.