A Summer Affair by Amanda Brookfield
Nicholas is in his early forties, has been married for nearly twenty years to a wife he still adores. Kate is lively, vibrant, enthusiastic; Nicholas feels old, decaying, ineffectual. How can someone like her possibly still love a man as depressing as him? Kate, who does love Nicholas - enormously - has noticed that her husband's unhappy but he won't tell her why. Her response is to be especially loving when she's with him, and to keep very busy so she doesn't have to be with him as often as before. Thus are the seeds of disharmony sown, because Nicholas, of course, is now convinced that Kate is having an affair...