Cloud Atlas
I read the book a few months ago. I really liked the book. I found the writing to be entirely engaging and I felt the themes that ran through each story were strong. However I always had the feeling I didn't get the point. I didn't understand what the overall connection was. Maybe I was thinking about it too literally.
The movie, for me, was a justified product because it allowed me to understand exactly how each story is connected to each other in a more tangible way. Well... maybe tangible is the wrong way to describe it because it's not tangible in a lot of cases.
I really enjoyed how the movie intercut the various stories together and connected key moments to each other. Some of the connections were a little weak and I don't know if they were meant to be viewed as mirrored events between the stories but it worked for me.
The Wachowski bros did a pretty damned good job of adapting this to the film. The book is such a dense story that I wouldn't have imagined how it could have been done. They managed to do it and yes, they did drop a lot of elements from the story. Entire side-plots are dropped and the main plot condensed, however it feels in benefit for the medium since they don't have enough time to setup those aspects.
I would be interested in hearing the opinion of someone who watches this and hasn't read the book. While I felt the movie helped me better understand the story, without knowing the basic plot beforehand I can see the movie being incredibly confusing.