The Charming Quirks Of Others (Isabel Dalhousie #7) by Alexander McCall Smith

As well as its advantages, there are drawbacks to the enlightened village that is twenty-first-century Edinburgh, where every Saturday night ears burn at dinner parties across the city, and anyone requiring the investigative abilities of a philosophical soul knows where to find her. Jillian McKinlay -- wife of a trustee of an illustrious school -- is the latest petitioner; she asks Isabel to look into a poison-pen letter that makes insinuations about applicants for the position of principal. Isabel's niece Cat has another new boyfriend who seems too good to be true. And when a pretty cellist with a tragic story takes a fancy to her husband-to-be, Isabel finds herself contemplating an act of heroic and alarming self-sacrifice.