– Robert De Niro has played so many creeps — Travis Bickle in “Taxi Driver,” Al Capone in “The Untouchables,” Max Cady in “Cape Fear” — that you wouldn’t think a bookish investment adviser would end up being one of his most bone-chilling characters.

But consider that the contender is Bernie Madoff, architect of a $65 billion Ponzi scheme, who seemed to do little more than shrug as his victims lost their life savings and his oldest son committed suicide.

“Let me ask you a question,” De Niro’s character wonders aloud near the end of “The Wizard of Lies,” an unsympathetic examination of Madoff’s downfall, premiering Saturday on HBO. “Do you think I’m a sociopath?”

For Diana B. Henriques, the New York Times journalist who wrote the book that the film is based on, the answer is obvious — but misses the point.

“I don’t think you can conduct your life with such a lack of empathy for the devastation you’re causing and not meet that fairly spongy definition of sociopath,” said Henriques, who appears as herself in the Barry Levinson-directed film that also stars Michelle Pfeiffer and Hank Azaria. “But it doesn’t explain anything to say he’s a sociopath. What you need to understand, and what I think you’ll see in Bob’s performance, is how plausible con men like that are, how utterly they can seize your trust and your imagination and make you believe.”

Ask De Niro himself to break down his interpretation and he’s about as verbose as Vito Corleone in “The Godfather Part II.”

“There’s a disconnect somehow in him that I still would like to understand,” he said earlier this year. “I did as best I could, but I can’t. The only thing I do feel strongly about is that he didn’t tell his kids and he didn’t tell his wife. But everyone around him probably had an idea. They just didn’t want to look too deeply because they knew something wasn’t quite right.”

De Niro may not say much in interviews, but his performance speaks volumes, particularly in a party scene when he forces his eldest to swap out his steak for lobster, even though the son has no appetite for shellfish. Later, as he is serving a 150-year prison term, he seems on the verge of confessing his sins to Henriques, only to redirect the blame to just about anyone except the prison guards.

In last year’s ABC miniseries “Madoff,” Richard Dreyfuss attempted to infuse at least some angst into the huckster’s persona. De Niro opted not to take a guilt trip.

“He’s a classic example of somebody who receded very much back, let people come to him and got to a position where people would think it’s an honor for him to take their money,” De Niro said. “That’s a classic, classic con situation that you see in all forms, in all walks of life.”

De Niro did not meet with Madoff before filming began, but he didn’t shirk on preparation. The two-time Oscar winner rarely does.

“We’ll go over stuff in preproduction and talk about things,” said Levinson, who previously directed De Niro in “Wag the Dog” and “Sleepers.” “And then he’ll be trying on a jacket or something. Step by step, very slowly, this character starts to emerge. It’s not like one day. It just keeps evolving. And then there’s the day when suddenly there’s the character he’s going to play. I’m fascinated every time I see the transformation.”

Henriques, who participated in the re-enactments of her prison interview with Madoff, compared the actor to a vacuum cleaner, sucking up every excruciating detail she could give him. After a scene in which the two of them improvised questions and answers, she better understood why De Niro is considered one of the greatest actors of his generation.

“I made the vow right then and there to never take investment advice from Bob,” she said. “Just in case he’s channeling his inner Bernie.”