Movies narrated by writers usually get a bit word-drunk, and so it is for much of "Being Flynn." Written and directed by Paul Weitz from a memoir by Nick Flynn, it's about the exploits of unpublished novelist Jonathan Flynn, played with seedy charisma by Robert De Niro. Jonathan shares narrating duties with his son, Nick (Paul Dano), a weedy would-be writer withering in the shadow of his absentee father's self-proclaimed genius.

Their voiceover tug-of-war raises the question: Whose story is this? Their relationship is so densely knotted with discord and yearning, even they can't see where one ends and the other begins.

It's been ages since De Niro tackled a character as rich and challenging as this, and he tackles it head-on. The old man ranks himself with Twain and Salinger as one of America's greatest writers, and the film teases us with hints that his long-gestating manuscript might be the real deal. A part of Nick wants to believe it. If Jonathan was a tormented master, that could explain the neglect that led to his wife's suicide, and his son's abandonment. At least then Nick's suffering would be part of a great artist's legacy.

When he's evicted from his apartment for attacking a tenant, however, we recognize Jonathan as a garden variety New York blowhard nut case. In a nice touch, his day job is driving a Yellow Cab; it's a thrill to see De Niro behind the wheel again.

The story brings father and son together at the homeless shelter where Nick works. "We catch 'em on the way down," says one of the shelter's workers. "Next stop, the morgue." The contrivance works because Weitz portrays the place and its clients with unsentimental, unflinching sensitivity. Following his father-son comedy-dramas "About a Boy" and "In Good Company," he approaches pathos here. Weitz charts Jonathan's slow spiral into destitution with clinical precision, each new split on his shabby coat reflecting another dehumanizing scar on his dignity.

The Flynns manage to achieve a degree of acceptance, not a pat reunion. They exist on different planets, but they still feel a gravitational pull. The understated Dano and forceful De Niro feel worlds apart, too. Their awkward banter is the stiff conversation of near-strangers. In flashbacks, Julianne Moore plays Nick's mother with such tenderness and grit that it's clear how she held the family together. Without her tough love, both Flynns labor to rewrite the messy narrative life handed them. It's the project of a lifetime and at the finale it's still unclear whose version will prevail.