The Lonely Silver Rain by John D. MacDonald. This title is the last Travis McGee novel published 1985. It is perhaps the most "libertarian" novel of the series with its rants against the War On Drugs, the societal cost of a government currency, the price of cultural decline with economic development, and the depression that often goes with growing older, being a survivor.
The plot is rather convoluted, worthy of Raymond Chandler, and the dialogue could be better, but the story gets at the heart of the corruption that was the 1980s. MacDonald has an insight into what makes people tick, and this motivation is not a good one. You are on your own.