As open season on Oscar prognostication draws to a close, award chatter reliably shifts to a discussion of which contenders will stumble in the final rounds. This year is no exception, though the final focus lies just as much on the films themselves, with a number of the most vaunted contenders ending last year on controversial, unexpected or downright puzzling notes.

The final reel of Ethan and Joel Coen’s “No Country for Old Men” has prompted fierce debate among critics and on Internet forums. Spending the opening stages of the film building tension to almost unbearable levels, the Coens then bring the suspense to an unexpectedly premature halt, leaving the film’s few remaining characters left to ponder the consequences in a quiet, meditative third act.

Speaking to Variety, Joel Coen attributes the film’s structure to its source material, Cormac McCarthy’s novel.

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“The novel works a certain way,” he says, “where you think the story’s about one thing, and then (McCarthy) basically pulls the rug out and you’re forced to think, ‘Well, then what is it about?’ ”

That unusual structure was something that attracted them to the story. “The fact that the main character gets killed offscreen halfway through the movie, and the turn the story makes, certain people want a more conventional ending, but I don’t think that would have been very interesting to us at all.”

Similarly, the titular main event in “The Assassination of Jesse James by the Coward Robert Ford” occurs relatively early in the film, leaving its characters with an entire third act in which to mull over the implications. As the former James Gang members stage a vaudeville tour re-enacting their exploits, the entire enterprise veers toward the farcical.

For this, director Andrew Dominik also sticks to his source, Ron Hansen’s historical novel.

“I think the main thing was, the book was an attempt to tell … a truer story of the assassination,” Dominik says. “Because it’s an attempt to create these people realistically, it’s different from your usual John Ford-type Western.”

Comparisons could be made to Martin Scorsese’s “Raging Bull,” in which boxer Jake LaMotta leaves the ring fairly early in the film, the remainder of which functions as an elongated coda, chronicling his decline into a bloated would-be comedian. Enviable company, certainly, though “Raging Bull” was infamously shut out for director and picture honors.

Some critics were also put off by the close of “Atonement,” which in the final minutes employs Vanessa Redgrave to deliver a narrative sleight of hand that calls the veracity of everything that preceded it into question. As the New Yorker’s Anthony Lane put it in his review: “(Redgrave’s) last, beneficent lie made me look back over the expanse of the film and realize, to my dismay, that I hardly believed a word of it.”

Much like “No Country,” “Atonement” is also derived from a decidedly literary source, and its ending retains the spirit of Ian McEwan’s novel, if not quite the letter, providing what the Boston Globe’s Ty Burr likened to “a final click that satisfies while refusing to console.”

That description could easily apply to the other films mentioned above, all of which hewed closely to their sources.

Fidelity to challenging source material is hardly a given in Hollywood. In 1939, William Wyler’s best picture-nominated “Wuthering Heights” adaptation omitted the entire second half of Emily Bronte’s novel, transforming her dark saga of generational grudges and obsessions into a swoonworthy Victorian romance; likewise Stanley Kubrick’s adaptation of Anthony Burgess’ “A Clockwork Orange,” which skipped the novel’s coda entirely, and best picture contenders like “From Here to Eternity” and “Peyton Place,” which offered simplified versions of difficult novels.

One also has to wonder if Oscar voters haven’t been more inclined as of late to honor films that end with a bang, such as “Titanic,” “Braveheart” and “The Lord of the Rings.” Paul Thomas Anderson’s “There Will Be Blood” would certainly fit that criteria, closing with a shocking outburst of violence. But while explosive, that sequence has also left more than a few heads being scratched.

Appropriately, watchers will have to wait until final reel to see what late twist Acad voters will give to this unpredictable year.