No one can accuse “Cloud Atlas” of lacking ambition: Clocking in at nearly three hours and weaving together six disparate storylines (with cast members playing multiple roles, often while crossing gender and/or racial boundaries), this is a rare American film that demands attention, even concentration.

It’s the kind of challenge that spawns rabid admirers and equally fervent detractors, although I must say I find myself somewhere in the middle. It’s a puzzle I enjoyed piecing together, but when each tale came to a close and built up to what was intended to be a soaring, emotional climax, I felt no flutter in the chest or tingle up my spine. I absolutely admire this adaptation of David Mitchell’s novel as an impressive object, but it never moved me.

If nothing else, making a movie this intricate -- densely populated, yes; impenetrable, no -- in an age of shortened attention spans and multiple-screens-at-once viewing habits constitutes an exceedingly bold move by directors Lana and Andy Wachowski and Tom Tykwer. “Cloud Atlas” throws viewers directly into the deep end and relies upon the viewer’s ability to stay afloat.

Also read: Tom Hanks Explains What 'Cloud Atlas' Is About (Video) [5]

Tom Hanks, Halle Berry, Hugh Grant, Jim Broadbent, Jim Sturgess and Doona Bae are just some of the performers who pop up in various roles over the film’s interconnected vignettes: A slave saves the life of a would-be slave trader during a 19th century ocean voyage. A scandalous young composer in the 1930s risks what’s left of his reputation to keep an older colleague from stealing his work. A ’70s investigative reporter uncovers disturbing information about a nuclear power plant. A modern-day publisher plots to flee the nursing home into which he has unwittingly committed himself. A waitress of the future escapes corporate captivity and foments revolution. A post-apocalyptic hunter-gatherer guides an advanced life form through an investigation.

There’s as much or as little here as audiences want to dig up, whether you look at the story as a fable about reincarnated souls seeking the highest plane of existence or merely a set of stories about fighting oppressors (nearly all of whom are played by Hugo Weaving) and discovering the power of love in an otherwise bleak universe.

Separately, the Wachowskis and Tykwer (each take on three of the six stories, but the mixture is seamless) rank among the contemporary cinema’s most dazzling visual stylists, and their collaboration does not disappoint. From the period tales to the eye-popping visions of the future, “Cloud Atlas” always offers something rich and fascinating to look at and listen to. (Oddly, it’s the contemporary section that impresses the least, partially because it’s a wacky farce nestled in awkwardly among more serious stories.)

This kind of parallel storytelling is nothing new, of course; it dates back at least as far as D.W. Griffith’s epoch-spanning “Intolerance” and as recently as Bill Forsyth’s failed “Being Human.” But the elaborate lengths to which this game cast (which also includes Susan Sarandon and Ben Whishaw) goes to inhabit such a wide field of characters puts this movie on a level of its own. Many pundits will no doubt connect the actors’ gender-bending with the recent life events of Lana Wachowski, but as the most famous transgender filmmaker in the world, she’s no doubt ready for those easy observations.

For all of the triumphs of “Cloud Atlas,” I just wish it maintained its power through to the end. You can tell when a comedy wants you to laugh, and when a tear-jerker wants you to cry, and it’s clear throughout the final act of this film when it wants you to be moved, to feel some accumulated emotion from this elaborate construction, and for me, it didn’t happen.

Nonetheless, “Cloud Atlas” is the kind of film that drives discussion and could even advance the medium, particularly if mass audiences are willing to give it a chance, especially on the big screen. Even its shortcomings wind up being more interesting than many recent successes.