For more than a hundred and fifty years Charles Dickens’ “A Christmas Carol” has occupied a central place as the holiday classic par excellence, and it’s not surprising that it has spawned innumerable screen versions—good, bad and indifferent. Les Standiford’s 2008 book aimed to uncover the story behind the book’s composition, and now screenwriter Susan Coyne and director Bharat Nalluri have adapted it as a film. Unfortunately the result, though it sticks to the basic facts, is so desperate to entertain and warm the heart that—if you’ll pardon the expression—it degenerates into cinematic humbug likely to satisfy only undemanding audiences.

The conceit of “The Man Who Invented Christmas” is that Dickens, coming off a series of relative flops in 1843 and in increasing debt, regains his status as England’s most popular writer (along with affection for the dissolute father he’d always held a grudge against) just as Scrooge rediscovered his humanity in the story the author was writing. Not only that: the tale’s celebration of the rituals of Christmas—and its invention of a few new ones—energized the public embrace of the holiday, helping to turn it into the massive business it is nowadays.

The way that Coyne and Nalluri have elected to portray the creative process is to have Dickens (Dan Stevens, in a performance so frenzied that it’s exhausting to watch—true, Dickens completed the story in a matter of mere weeks and had it quickly published, but Stevens is like a human version of the Energizer Bunny), be inspired by a variety of factors—the names and faces of people he meets on the street, the circumstances of his own family (a crippled nephew becomes Tiny Tim), a speech he gives on behalf of the poor in Manchester (where a bit of conversation becomes one of the story’s most famous lines), dreams and painful recollections of his own past, when his father’s indebtedness got the twelve-year old sent to work in a bootblack sweatshop to toil in misery, and the ghost stories told to his children by their new Irish maid Tara (Anna Murphy).

Moreover, as the tale emerges in Dickens’ mind, the characters come to life and follow him about. Chief among them, of course, is Scrooge (Christopher Plummer, predictably fine), supposedly based on an irascible old fellow the author saw (or dreamed he saw) as the sole “mourner” at the nocturnal funeral of an equally miserly colleague. The two will bicker and debate as other elements of the tale fall into place, with most of the new characters joining the entourage following Dickens about as he argues with his publishers, gets sympathy and help from his friend Forster (Justin Edwards, looking like a Stephen Fry stand-in), deals with illustrator John Leech (Simon Callow, doing his grumpy routine) and enduring the feigned commiserations of the novelist Thackeray (appropriately snooty Miles Jupp).

Even more important to the book’s genesis, however, are Dickens’ relations with his own family. Not so much his affection for his children, a large brood on point of getting even larger, or his wife Catherine (Morfydd Clark)—who is presented as endlessly supportive, though in real life they seem to have been a more contentious couple—but his tense feelings toward his father John (Jonathan Pryce), who arrives in London unexpectedly with Charles’ mother Elizabeth (Ger Ryan). John is portrayed as a lovable rascal always in search of a loan or a handout, whose troublesome presence irritates his son to no end.

The big last-act breakthrough involves that old standby, writer’s block (Dickens supposedly can’t imagine a happy ending). That’s not an obstacle for the filmmakers, however, who conveniently link Scrooge’s redemption to Charles’ change of heart toward his father, whose lack of responsibility he has never been able to forgive. Once he does so, the conclusion of the book takes shape and the rest is publishing history—as well as familial harmony (although, it should be noted, Dickens and his wife will eventually part ways).

The failing of “The Man Who Invented Christmas” isn’t so much the premise as the execution. The notion of linking Dickens’s writing of the book with his own troubled background—and his commitment to bringing the plight of the poor with a cruel industrial society to the attention of the British public—isn’t at all a bad one. But by fashioning it into a gaudy crowd-pleaser that reduces Dickens’ achievement to a simplistic psychological cliché Coyne and Nalluri undervalue his genius and underestimate the audience’s intelligence. The picture might work as an exercise in calculated sentimentality, but it lacks the heart of “A Christmas Carol”—the book’s social consciousness. Dickens manipulated his readers to bring about change; these filmmakers manipulate their viewers merely to extract some easy tears (and perhaps a measure of smug self-satisfaction over their knowledge of the book—which, it must be noted, the screenplay assumes).

Still, there are pleasures to be had here, if one gets past Stevens’ overly busy performance and Pryce’s insistence on trying to be endearing. Plummer underplays cleverly, savoring his best, most mischievous lines (one would like to see him actually do Scrooge—he might actually give Alastair Sim a run for his money), and the supporting cast includes plenty of colorful players (Miriam Margolyes, as the Dickens housekeeper, is always a delight). Paki Smith’s production design and Leonie Prendergast’s costumes are fulsome, and Ben Smithard’s widescreen cinematography lustrous (though Mychael Danna’s score is, like Stevens’ manic turn, overemphatic).

“The Man Who Invented a Christmas” is like a box of colorful candy, much too sugary and not at all nutritious. Its chance of becoming a holiday perennial itself is pretty slim.