After all these years, some folks — including critics, who really ought to know better — still insist on judging movies on whether they “did justice” to the books from which they are adapted. You know the line: (Your favorite author) would turn over in his grave if …

Sorry, but, ultimately, that ‘s irrelevant: film and fiction, while both about storytelling and both having something to do with the power of language, are two radically different art forms, and it’s wrongheaded to evaluate a movie on how faithful it is, or isn’t, to the book. Who cares what the author thinks, or would think, or whether his or her totally devoted fans approve?

With “The Great Gatsby,” Baz Luhrmann impressively captures the over-the-top Jazz Age craziness and decadence swirling around Jay Gatsby (Leonardo DiCaprio), the mysterious West Egg, Long Island millionaire who lives next door to striving  Wall Street trader Nick Carraway (Tobey Maguire); the latter had literary ambitions before he opted to chase the big money that was being made pre-Crash. In an extraneous element not present in the F. Scott Fitzgerald novel, the story is framed by Nick’s after-the-fact sessions with a therapist, who encourages his patient to write about his exhilarating and then traumatic experiences among the nouveau riche and old-money elitists on Long Island.

The first half of the film is all gaudy, zippy, over-the-top excess, dazzlingly captured and perfectly fitting in terms of Luhrmann’s intent with the film. Against the spectacle of enormously extravagant, all-night parties, replete with ever-flowing champagne, dancing girls, roving bands of musicians, and fireworks, in a cavernous mansion resplendent with fountains and swimming pools, Fitzgerald’s characters are introduced: Gatsby, a grown-up poor boy grown impossibly wealthy through unsavory connections with Meyer Wolfsheim (Amitabh Bachcha) and other crime-world figures; Daisy (Carey Mulligan), Nick’s cousin and Gatsby’s long-lost paramour; Daisy’s husband Tom (Joel Edgerton), Daisy’s golf-pro friend Jordan (Elizabeth Debicki); Tom’s ill-fated mistress Myrtle (Isla Fisher); and her hard-working husband George (Jason Clarke).

The second half of the film largely abandons the first section’s speedy edits and fast pace (although the cuts, thankfully, aren’t as quick nor is the pacing as frenetic as in Luhrmann’s “Moulin Rouge!”).

Clearly, the film is a product of the director’s vision as much as or much more than Fitzgerald’s. Luhrmann took the bones of the story and created an entirely new experience that’s striking and works on its own terms: it’s far more of “an amusement park,” as Nick says of Gatsby’s parties, and even a thrill ride, than was the ’70s Redford version, and more than one might have expected from an adaptation than the novel. And yet the movie still manages to effectively address some of the big themes — identity, alienation, the dark side of the American Dream — explored by Fitzgerald. Rather than rolling over in his grave, it’s not impossible to think that the author might be gladdened to discover that the themes he mined remain viable as touchstones in a major movie.

The production design, cinematography and visual effects are often stunning, the music — from Gershwin to Jay-Z to Jack White — is invigorating, and the performances, particularly those of DiCaprio, Mulligan, and Edgerton, are often impressive; Maguire is a bit too passive to quite strike the right tone as Carraway. It’s nice to hear portions of the novel in the screenplay and, in one case, projected on the screen.

I caught both the 3-D and standard versions, and I’d recommend seeing the 3-D — it’s the way the director created the film to be seen, and the technology really allows one to become more fully absorbed in Gatsby’s world. Fascinating place to visit, at least for a while.