story identification - What poetic old detective noir book has mutants smuggled out of a ghetto being blackmailed?

Years ago I read this old science fiction book that was written in a poetic noir style, and I remember bits of the plot, but not any names to google. Could you help me find it?

It was from my Dad's collection which means pre-2000 for sure, and probably pre-90s, in fact, I'm pretty sure its pages were turning yellow. Unfortunately I now live on the other side of the continent from him and his collection, and I can't ask him to look through his rather substantial library based on a plot without a title or author.

The plot as I recall it: There was someone murdered, and they had a connection to someone rich, an ex-military figure. The police no longer investigate crimes if no one is willing to pay them, so they hand it over to a PI (the main character) in exchange for a commission if he finds someone willing to pay him to solve it. Then they tell him that someone powerful has told them to lay off, and retract the case from him. I forget the next bit but it eventually winds up going into a ghetto for mutants, and saves himself at one point by pretending to be a mad berserker by reciting nursery rhymes. When he gets back out he finds out that the powerful person he is investigating has been smuggling mutants out of the ghetto, letting them get to positions of power and then blackmailing them for huge sums of money. Oh, and the bad guy was a (super-intelligent?) mutant himself I think. There was a final fight in a factory or something?

What caught me was the silly, overwritten style; it wasn't even a particularly good book, but the writing style was very distinctive, a sort of parody of the noir genre sort of like when Calvin does his noir stories in Calvin and Hobbes. Everything was described with metaphors and similes out the wazoo.

Books that have been suggested elsewhere that it isn't: Altered Carbon, by Richard Morgan (too recent, plot doesn't match); Gun with Occasional Music by Jonathan Lethem (No talking animals in my book).

Answer

Ha, I know this one! The book you want is, Hot Time In Old Town, by Mike McQuay. It's the first in a series of 4 books about Mathew Swain, 21st century Private eye.

The Mathew Swain series – Hot Time in Old Town (1981), When Trouble Beckons (1981), The Deadliest Show in Town (1982) and The Odds are Murder (1983) – derives from the works of Raymond Chandler (1888-1959) and Chandler's direct successors. As the series develops, Swain fights corruption first on Earth, then on the Moon and then on Earth again, always finding fit targets in the organizations which dominate society.

Here's a couple of excerpts from Hot Time in Old Town:

"Venitas Boulevard was a carnival as I hummed my bullet through its misty innards. Midday whores, young ones who had to look good in the light of day, roamed the jungle paths looking for lunch money. Lean, tall studs in color-changing tunics and street-parade hair red as West Texas mud, prowled like panthers; their heads set firm, and their eyes ever watchful. Pack hunting brown cubs with black, tangled manes and guts full of government dope leaned against the hulking ruins of dead brownstones and called with primal elegance to those unfortunate enough to be passing by. It was Tuesday—garbage day."

and:

"He lives in Old Town. He has a sort of underground railroad to help the crazies get out of there."
"You mean, he smuggles mutants into the city?"
"Interesting world, isn't it?"
"How?"
"The ones who look . . . normal. The ones who can pass. He gets them new identities, or pays people to raise the children as their own. We help on the transportation end sometimes.''

http://www.amazon.com/Hot-Time-Town-Mathew-Swain/dp/0553148117