The adaptation of the philosophical book by Britain's David Mitchell premiered at the Toronto International Film Festival to sharply divided reviews, suggesting the complex storylines and ambitious plot structure did not always connect with audiences who had not read the novel.

With a budget that reportedly topped $100 million, and an all-star cast of Tom Hanks, Hugh Grant and Halle Berry playing multiple roles, the pressure is on for "Cloud Atlas" to be a box office hit. And with Hollywood awards season just around the corner, anticipation is running high.

Co-directed by Tom Tykwer of "Run Lola Run" fame, and the sibling team behind "The Matrix Trilogy", Andy and Lana Wachowski, "Cloud Atlas" is made up of six narratives spanning from the 1840s to the present day to a post-apocalyptic future.

The century-hopping film explores how actions can have consequences in the past, present and future, and the notion that humanity cannot help but repeat itself.

While Mitchell's book tells six separate but linked stories in chronological order, moving from the past to future and then back again, the film intercuts the stories to drive home the link between the threads.

"When you read the book you see that there are very resonant themes in all six stories," co-director Lana Wachowski said of the adaptation process at a news conference on Sunday.

"Once we started seeing the resonant pieces of narrative and the pieces of narrative that seemed connected, we began sort of laying it out as if it was one big story and that was our goal."

GIANT FOLLY OR INTENSE MENTAL WORKOUT?

Britain's Guardian newspaper gave the film two stars, saying it "carries all the marks of a giant folly, and those unfamiliar with the book will be baffled."

"Yet it's hard to wholly condemn the directors' ambition - this is fast-paced and cleverly assembled, with the best of the performances shining through the prosthetics," the Guardian said.

Variety said the movie was "an intense three-hour mental workout rewarded with a big emotional payoff," while Indiewire called it "bold, messy and disappointingly unimaginative."

The actors undergo several big physical transformations in their various roles.

Hanks is a shady doctor in the 1840s, a nuclear scientist in the 1970s and then a simple valley-dweller in the distant future, while Hugo Weaving (Agent Smith in the "Matrix" films)switches from a hired hitman in the 1970s to an iron-fisted female retirement home nurse in the present day.

The Hollywood Reporter called the film "an impressively mounted, emotionally stilted adaptation" in a review that highlighted the editing and acting. But it lamented "there are so many characters and plots tossed about that no one storyline feels altogether satisfying."

Slant magazine was even harsher, calling the film "a unique and totally unparalleled disaster."

Despite the challenging content, Hanks said that doing the film was a no-brainer for him.

"It's kind of like a hug that gets tighter and tighter," he told reporters on Sunday. "By the time I was reading the last 40 or 50 pages of the screenplay, I was completely involved in each of the individual struggles and understood that these were characters that were having to make the choice between cruelty and kindness, and that decision was going to change the world from thereon in."

"And it was totally worth it if only to see Hugh Grant as a cannibal," Hanks added with a grin.

(Reporting by Julie Gordon; editing by Jill Serjeant and Mohammad Zargham)

• A Permanent Economic Emergency