Atonement was widely praised by critics, garnering a metacritic score of 85 out of 100 and 7 Oscar Nominations, and strongly disliked both by The Critic (http://movies.nytimes.com/2007/12/07/movies/07aton.html)
and by several people I know who saw it. Having now seen it, it's hard for me to understand either reaction. While far inferior to Ian McEwan's original novel, Joe Wright's heritage picture follow-up to his heritage pic Pride and Prejudice succeeds in bringing McEwan's fascinating pre-WWII/WWII story and characters to life. Along the way, it introduces Scottish stud James McAvoy to an even larger audience, and, quite unbelievably, manages to not be completely ruined by the presence of Keira Knightley. There are few movies capable of not being ruined completely by Keira Knightley, so Wright deserves that much credit - even if he's to blame for her casting.
McEwan's novel is about both a romance between a lower-class intellectual and a young rich girl being interrupted by her younger sister's lie, and the difficult and complex moment of modernism and stream-of-consciousness in British literature that took place between the wars, played out in the younger sister's attempts to tell the story of that romance. That the film largely ditches the latter subject is to its credit; although it eviscerates McEwan's story, any attempt to render the novel's interiority would have been nearly impossible. Instead, Wright sticks to a fairly standard tale of star-crossed lovers, taking place in a lavishly filmed British mansion, a World War II hospital, and, in both the novel's and the film's finest sequence, captured France, as our protagonist Robbie tries to make his way to the evacuation point at Dunkirk. It does none of these things phenomenally, but it does none of them poorly, and if you're a fan of Oscar-bait heritage pictures (The English Patient, every Merchant and Ivory film, etc), than this one's for you.