Burn After Reading” implies one of those spy thrillers that keeps everybody guessing about who everybody really is, featuring tense drama, split-second timing, thrilling chase sequences, and highly intelligent secret agents operating at the peak of their professional powers.  Well, “Burn After Reading” is kind of the opposite of all that.  Oh, we start at the CIA, all right, where a mid-level operative named Osborne Cox (John Malkovich) is summarily fired for having a drinking problem.  He departs only after an indignant, profanity-laced tirade, but that is only the beginning of his difficulties.  His cheating wife Katie (Tilda Swinton), told by her lawyer to pilfer the computer files before filing for divorce, inadvertently copies some of Osborne’s CIA stuff on to the disk, which then inadvertently falls out of her purse at the local fitness gym.  When the workers there find it, they figure that this is a golden opportunity to collect some easy money.  Linda (Frances MacDormand) wants cosmetic surgery, and she enlists the muscle-brained personal trainer Chad (Brad Pitt, whose comic airheadedness almost steals the show) to try to put the squeeze on Osborne.  But then it turns out that Katie’s lover is the same as Linda’s, Pretty Boy Harry (George Clooney), whose wife is also having him followed so she can divorce him with cause, and just when we thought things couldn’t get any more messed up, well, they do, anyway.  What’s so enjoyable about this film is the preening pleasure of wat ching the deflation of the self-important.  The language alone deserves the R rating, not to mention the indelicate contexts, so leave the kids at home, but the grown-ups will delight in the latest Coen Brothers’ version of chicanery and buffoonery.