Cloud Atlas is a really terrific book, and an utterly garbage movie. Nevertheless, I feel that this trailer describes the content and its structure very well-- that is, Cloud Atlas is sprawling, ambitious, and is structured into six stories within one another like a Russian nesting doll. There are shared characters and many through-lines, which the directors tried to replicate by having a small group of actors play all of the major characters. That is not a bad idea in theory, and I think for the antagonist roles it works rather well. But for some reason they decided that this should involve a lot of race-swapping, which is never a good idea. So by all means, watch 'Cloud Atlas' if you want to see Halle Barry in Twilight-style whiteface (you don't), or better yet, read the novel, which is brilliant and stunning and riveting and has no race-swapping of any kind.