Keira Knightley and James McAvoy in AtonementATONEMENT

It seems that lately, whenever I leave the film version of some well-regarded or beloved novel - be it No Country for Old Men or Gone Baby Gone or one of the Harry Potters - I feel a nagging guilt for not having previously read the books they're based on, and I'd consider remedying that if I wasn't concerned about being subsequently disappointed by the adaptations. (Or, in the case of most of the Potter movies, even more disappointed.) After seeing director Joe Wright's Atonement, though, I was completely annoyed with myself for being unfamiliar with author Ian McEwan's 2001 precursor - I was dying to understand what, when the end credits rolled, inspired a majority of my fellow audience members to applaud.