It is, after all, their first night as a married couple and all roads lead to what’s supposed to happen on that mattress. Both Florence and Edward are understandably awkward to varying degrees, but as the evening progresses it becomes apparent that one of them is just not ready — and may never be ready — for the supposed bliss of getting between the conjugal sheets. Edward is a history grad student from a working class family whose mother (Anne-Marie Duff) has brain damage but whose household is still a loving one — even if his future mother-in-law sniffs at them a bit. Edward likes rock music, is more outgoing and occasionally too impulsive, while Florence is a budding political activist who nevertheless has a reserved air about her — and a secret which is glimpsed only fleetingly as their love affair comes to a, shall we say, premature ending in that room on Chesil Beach. Theater director Dominic Cooke, making his debut behind the camera here, manages to take what many have deemed an unfilmable piece of writing (because of its internalized nature) and turn it into a largely compelling look at those icy British attitudes toward sex and class in the days before the sexual revolution and the vaunted “Sixties” really turned things upside down. The damage done to both Florence and Edward by their respective histories becomes palpable, thanks in no small measure to terrific performances from both actors. The only thing that On Chesil Beach really fumbles is its final stretch: while the book’s closing pages are all in the thoughts and ruminations of one character, the movie makes it all too literal and utilizes some truly bad old age make-up to make it even more cringeworthy. To be fair, it’s certainly not easy to visualize any ending to this tale that works in a cinematic sense, but perhaps McEwan should have brought in another screenwriter to help him, unlike his poor protagonists, reach a satisfying climax. On Chesil Beach is out in theaters Friday (May 18).