Delicacy - David Foenkinos

He was passing by, she kissed him without thinking. Now she wonders whether she did the right thing. But Natalie isn't certain of anything anymore. One minute she was a happily married young woman, successful in her career, and convinced the future was full of promise. But when her husband was run over by a car, her whole world was turned upside down. Years later, still bruised with grief but desperate to move on with her life, she impulsively kisses her colleague Marcus.
For Natalie, the kiss is just a gratuitous act. For the awkward, unassuming Marcus, it is the moment at which he falls hopelessly, helplessly in love. But how will he ever convince such a beautiful, intelligent but confused young woman that he is the man who can bring her back to life?