So there are really two ways to look at Cloud Atlas, The Movie. The first is on it's own merits as a movie, and the second is as an adaptation of a work I really, really like. They're somewhat intertwinned, but film is a different medium and requires different skills to get a story across, and so I'm not going to quibble about the large amount of plots dropped from each time period, because the damn thing is already 3 hours long.
The film opens with Tom Hanks in a distant future narrating his younger self in a slight-less-distant future, setting up the "post-apocalypse" storyline, and then flashes around the other 5 time frames introducing the main set ups. Going backwards we have Dystopian Future Korea, 2012 London, 1970s San Francisco, 1930s Edinburgh (I was confused for a moment because it's Belgium in the book), and 1840s Pacific Islands. This is actually the hardest going part of the movie, as it flashes around with settling anywhere to get traction, and without the dazzling compression of say, Speed Racers, opening, which was the best and most innovative part of it. The film then continues to jump between each period as it goes along, lying events alongside each other as they go.
It's a neat device, actually, especially when it "pairs" timelines for a short period to mirror the thematic beats. It's not always smooth - sometimes its heavy handed, or jarring, and sometimes you just want a little longer for a sequence to breathe, but on the whole it's a successful device. Less successful is the casting. One of the movies' gimmicks is to have the same cast working different characters in different periods, often as a different race or gender. It's most notable with Hugo Weaving, playing the "devil" in each period, but the problem with that is that it left me wondering if we are supposed to believe each actor has a linear connection through each story. And they clearly don't, so it becomes a distraction, even before the occasionally dodgy prosthetic is considered. I suspect if Weaving wasn't so consistently each periods villain, this would be a lot less of an issue.
All that said, when it's firing on all cylinders the movie really soars. The Wachowskis have always had a great eye for direction and cinematography and the movie looks stunning in every time period. The cast give it everything (even under the make-up) and there isn't a weak link in there. Some of them I'd watch whole films of, most notably Timothy Cavendish and Luisa del Ray. On the whole it's staggeringly ambitious, and mostly successful. It's certainly worth seeing, and I suspect a film that will earn a critical revisiting in years to come.
As an adaptation I do have some reservations. The first two sections especially, "The Pacific Journal of Adam Ewing" and "Letters from Zedelghem" don't feel too well served, at least in part because nothing too much happens in them, and that sort of internal narrative works better on the page. On screen, it just doesn't get enough time to work fully, so they end up reflections of the other stories, not stories in their own right. Both "An Orison of Somni-451" and "The Ghastly Ordeal of Timothy Cavendish" work really well, at least in part to strong central performances, and "Half-Lives: The First Luisa Del Ray Mystery" manages to be more engaging on the screen than I found on paper.
This leaves us with "Sloosha's Crossin' an' Ev'rythin' After", which has possibly been changed the most and acts as the movies bookends rather than centre. The main journey becomes one of hope for the future, contacting off-world colonies to come and rescue the remnants of humanity, and the movie's end is essentially one of unqualified happiness. We leave the old world behind, it seems to say, and become something better. Which is fine, but I liked the compromised ending of the book, with Ewing looking forward to building a better world who's end we've already seen, It's the only change which really stuck with me, to be honest, in a film that largely manages to condense a lot of material and keep it's spirit intact. So on that front, like the film - read the book too.