They call him Freakshow.

The real name of the hero of Edward Norton’s “Motherless Brooklyn” is Lionel Essrog, a name that has to be an anagram for something (good luck!). Everyone calls him Freakshow, though, because of the Tourette’s syndrome tic that finds him reacting to the things other people say by reeling off lists of similar-sounding words.

An acquaintance who is a Miles Davis-like trumpeter (played by Michael Kenneth Williams) compares Lionel’s riffing to jazz, where it feels like the music takes control of the improviser rather than the other way around. And, like a jazz musician, Lionel has found ways to harness his skill, which, coupled with his photographic memory, comes in handy when he’s solving cases at a small-time detective agency.

Norton, who wrote, directed and stars as Lionel, has been planning to make a movie of “Motherless Brooklyn” almost since part-time Maine resident Jonathan Lethem’s novel came out in 1999. The intervening years may explain why the character’s age seems to vary from scene to scene and why the plot of the movie isn’t that much like the inventive book, a detective novel where the biggest mystery is how the detective’s brain works.

Lionel is a youth in the book, but he appears to be in his 40s in the movie, which invents a mostly new mystery for him to solve: a story of urban corruption that, in its particulars, mood and solution bears more than a passing resemblance to the great “Chinatown,” except that its evil tycoon (Alec Baldwin) drips venom all over New York City in the 1950s instead of Los Angeles in the 1930s.

I wish the bones of “Chinatown” weren’t so evident. But if you’re going to nod to a classic thriller, “Chinatown” is a good one to pick, and “Motherless Brooklyn” has many other things going for it: The propulsive action scene that opens it. Dick Pope’s faded-photograph cinematography. Daniel Pemberton’s jazz score, which features Wynton Marsalis nimbly incorporating themes from Thelonious Monk and Charlie Parker. The atmospheric setting, which convincingly recalls an era when New York was being transformed by Big Money. A dynamite supporting cast, including Cherry Jones as a fiery city planner, Leslie Mann in a change of pace as a world-weary moll and Norton.

The writer/director/star’s subdued performance meshes perfectly with a screenplay that often recalls the worn-out patter of Raymond Chandler, as when Lionel says, “There is no use in lying to a woman who’s smarter than you.” (One great touch: The narration lets us into Lionel’s thoughts, where his tic doesn’t manifest itself.)

The main character is what makes “Motherless Brooklyn” special because the movie really is about inviting us into a stranger’s point of view. Lionel’s condition makes him riff on words because his brain is trying to make sense of the way strings of words sound. He cannot stop until it sounds right.

A similar impulse propels Lionel throughout the movie. He gets beaten up and betrayed but he continues charging ahead in the investigation of a friend’s murder because he cannot stop until he gets to the truth.