The characters in the story are connected by events throughout space and time, and the actors play multiple characters throughout the story to layer this idea of interconnectedness further. To my mind this movie is a lot like my limited understanding of String Theory and Quantum Physics - it's mind-bending, but there's a beautiful magic to it that we all can relate to. As you can see, my understanding of this movie makes only a little sense. Take my advice and throw sense out of the window (or at least suspend it) when you go to see Cloud Atlas, you'll have a much better time of it if you do.
Hugo Weaving's broad acting range has always been nothing short of astonishing in my eyes - especially as the title character in V for Vendetta, in which you never really see his face behind the Guy Fawkes mask, but you can feel the expressions he's conveying. In Cloud Atlas all his roles are somewhat sinister and remind you of him as Agent Smith in The Matrix. All the characters are quite silly when you think about it and they're all pretty serious about their silliness. Their stories are quite moving though. Tom Hanks, Halle Berry, Jim Broadbent, Hugh Grant, Jim Sturgess, Susan Sarandon, James D'Arcy, Xun Zhou and a handful of others join in on the costume fun, each portraying multiple characters.
Cloud Atlas is a beast of beauty; it's seemingly haphazard and all over the place in its narration of a visually appealing tale. I use the word seemingly because I'm not sure whether there is a method in the madness (the narration promises that there is) or whether I am missing the plot entirely. It's the sort of movie that's easy to slide into and allow your mind to be transported by. It sells you a plot that's difficult to make sense of once you stand up from your seat and leave the cinema. Whilst you're there, though, you buy into the magic and it all makes sense on a raw, emotional level. It's said (by some clever person) that a good book never reveals all of its secrets upon the first reading and that holds true for this movie, it begs to be viewed multiple times - it wants as much of your money as possible ;). Having never read David Mitchell's novel, on which the movie is based, I can't say whether or not it, too, had the same appeal to revisit its world.
I guess I must "warn" you that Cloud Atlas is a long movie, at approximately three hours.
My head is in Cloud Atlas and I don't want to find my way back down. It wasn't on my 2012 list of movies to look forward to, but it managed to creep (sneaky bastard that it is) onto the list and position itself in the top five. Go to see Cloud Atlas and allow it to transport you to and from time and space.