I first saw An Awfully Big Adventure on TV at two o'clock in the morning. It made very little sense, and I couldn't understand about a third of what was being said, but the movie still, as another reviewer succinctly put it, "hijacked my consciousness." It was subtle, honest, unforgiving, amazingly well-acted, and a lot of other good things that I can't find the words for right now.
I recently purchased a copy of the video, and realize now that while it loses nothing upon further viewing, An Awfully Big Adventure benefits greatly from a second watching. The dialogue becomes clearer the more you listen to it and the nuances of the characters and the story become more pronounced. Even though my first reaction to the film was favorable, I still think that one cannot judge this movie fairly after only seeing it once (although if you enjoyed it the first time, you probably will again). I have a feeling that nearly all of the reviews here are by first-time watchers, and while you shouldn't entirely discredit their remarks, keep in mind that, like most complex movies, An Awfully Big Adventure only gets better the more you watch it.
I also feel that it cannot be stressed enough that this is not a happy, uplifting movie. "Disturbing" is a word used often to describe it, but the word that comes to my mind is "uncomfortable." There's really nothing at the end of the film to redeem all of the sadness, as is common in most movies. Thus, if you don't like to watch depressing movies, DON'T WATCH AN AWFULLY BIG ADVENTURE. And if you're an Alan Rickman or Hugh Grant fan (both of whom are great) and insist upon seeing it, don't write a review that discourages others from watching it just because it was too dark for your tastes.
*I haven't read the novel of the same title by Beryl Bainbridge, but I've heard that it helps to clarify the confusing points in the movie, besides being a good book. Just a thought...