Among the dozens of stories Mary Gaitskill has published since her 1988 debut Bad Behavior, only one — “Secretary,” a detached BDSM narrative from that collection — has been loosely adapted for the screen. On its face, this fact is not entirely surprising. Gaitskill is, above all else, a prose stylist, renowned more for short fiction than her whipsawing novels, her characters prone to white-collar monotony and lurid sexual encounters. But if these themes have scared off Hollywood producers, they haven’t posed such obstacles for her closest peers, excavators of middle-American intercourse like John Irving and Joyce Carol Oates. In Gaitskill’s case, the sex isn’t the problem so much as its temperature, the hopelessness that precedes and follows.