It takes a lot of nerve and ego to adopt David Mitchell’s Cloud Atlas to the big screen. The novel tells six separate stories in six separate time periods, careening from the 19th century to a post-apocalyptic future. Each story riffs on a different genre, both in terms of plot and language. The unifying thread among them is physical text itself, a conceit that’s difficult to communicate through film. But these ridiculous, seemingly insurmountable challenges did not deter directors Tom Tykwer, Andy Wachowski, and Lana Wachowski from condensing the novel into a three-hour, visually imaginative epic. It’s inevitable that they wouldn’t be able to pull it off — how could they? — but the admirable material outweighs the mistakes.