“Indignation,” the latest Philip Roth novel to make it to the big screen, hangs on a trio of absolutely delicious if somewhat delusional confrontations — big scenes between its young hero, a secular Jew debating his Protestant academic dean about faith, privacy, sex and assimilation.

That hero, another version of Roth for those who read most novels by the “Goodbye, Columbus/Portnoy’s Complaint” author as at least a little autobiographical, is a self-possessed college freshman from Newark, standoffish, deep into the atheism of Bertrand Russell and able to hold his own with a senior academic despite being the 19 year-old son of a Newark butcher.

And the scenes — pitting Logan “Percy Jackson” Lerman against the actor/playwright Tracy Letts (“Killer Joe”), are laugh-out-loud marvels orfirony and dark comedy. Young Marcus Messner has asked to change dorm rooms. And Dean Caudwell uses their interview as an interrogation, to probe young Messner’s refusal to “learn how to get along with people,” to question his “tolerance” and to figure out what or whom Marcus turns to for spiritual comfort.

“I am sustained by what is real,” the kid declares, before launching into a defense of Bertrand Russell, an assault on the small 1950s Ohio college’s requirement that students attend chapel and umbrage taken at the dean’s assumption that the kid’s father is a “kosher butcher.”

The rest of “Indignation” isn’t much to latch onto. But these scenes give it heft, or at least entertainment value.

The big theme here is “even the littlest mistake” can have consequences. The Korean War is on, and Marcus goes to the funeral of a friend killed in action and meets others who are fodder for the draft. But he is off to college and its promise of a deferment.

That’s where he becomes smitten by Olivia Hutton, or “the unceasing movement of Olivia Hutton’s leg,” he narrates. She’s a bobbysoxer prone to sitting with one leg carelessly draped over a chair while reading in the library where Marcus has his student job. She’s blonde, and without saying it out loud, Marcus appreciates her shiksa appeal .

Because he wouldn’t. Marcus makes a big deal out of getting away from his smothering, stereotypical Jewish parents but not about the “coincidence” of being roomed with two other Jewish kids in the dorms, out of the dean’s assumption that his father is a kosher butcher but bristling at the notion that he is somehow “hiding” from his Jewish identity.

You know, that whole self-loving/self-loathing Philip Roth thing.

Olivia, the experienced and alluring gentile siren, is played by JCanadian starlet Sarah Gadon.

Their one and only real date ends with an unexpected and under-motivated (as far as Marcus is concerned) act of oral sex. And that so befuddles him that he puts enormous academic energy into figuring out why this happened, what is going on with her (“I think it’s because her parents are divorced.”) and how he should act around her.

And Olivia, showing a damaged vulnerability that suggests she’s a little off, takes that badly.

“One little mistake” has consequences, and they ripple into arguments with his roommates, debates with his dean and onward and outward.

The story, framed within a Korean combat scene, plays like a Proustian parody of 1950s potboilers as filtered through the Semitism-centric prose of Roth. Producer-turned-writer/director James Schamus hits his Roth-marks, but fails to make the material sing, or particularly relevant. It all feels dated and entirely too pat to be much of a challenge. 

But Lerman (“Fury”) is game and handles the wise-beyond-his-years/guilt-ridden Marcus with skill. Gadon has less to work with, but is gamely gamin when need be, and her Olivia is smart enough to keep Marcus on his heels.

And those scenes with Letts are worth the price of admission, even if the movie overall drags, dry and not nearly as droll as Roth must have intended.

MPAA Rating:R for sexual content and some language

Cast: Logan Lerman, Sarah Gadon, Tracy Letts
Credits: Written and directed by James Schamus, based on the novel by Philip Roth. A Summit release.

Running time: 1:50