Your reaction to the film version of Atonement, which opens December 7, may depend on whether you can be shocked twice by the same revelation.

Ian McEwan’s superlative 2001 novel starts with a fusty Victorian framework — a country house, an upstairs-downstairs flirtation and a mislaid letter — that McEwan soon charges with eroticism. The tale gradually expands into both a harrowing war story and a decades-spanning meditation on morality. Keira Knightley, who grows thinner in each movie and is now approximately the width of a parenthesis, stars with James McAvoy (who played Idi Amin’s doctor in The Last King of Scotland) in a sumptously decorated and expertly photographed vision of the novel directed by Joe Wright, who also guided her to an Oscar nomination for Pride and Prejudice a couple of years ago.

Wright’s Atonement is a fine effort that left me largely unmoved, possibly because the two greatest strengths of the book are absent. First is McEwan’s devastatingly precise and unnerving prose, which invariably makes you shiver at the terrible things that haven’t even happened yet and for which Wright has no real equivalent apart from a somewhat overused audio motif of a prewar typewriter’s keys slamming like ammunition being locked and loaded. Second is McEwan’s much talked-about pull-the-rug-out ending, which has little effect on you if you know it’s coming.

There’s a reason why surprise-twist stories rarely hold up well the second time around: You lose interest in the characters as people because you begin to see them as mere tools of the plot.