The Minotaur

Barbara Vine's mysteries aren't so much 'whodunnit' as 'whydunnit' - she usually frames her books as a present-day retelling of a past event, focusing more on how her characters interact than the actual events.  The Minotaur follows that pattern.  Cartoonist Kirsten Kvist is on vacation in Riva when she sees Ella Costway, a member of the family with which she lived when she first came to England from Sweden.  

As a university student in late 1960s Sweden, Kirsten fell in love with an English student and earned a nursing credential so she could follow him back to England.  He helped her find a job as a nurse/companion to John Cosway, a mathematical genius diagnosed with schizophrenia and living in the family home with his domineering mother and three downtrodden sisters.  It doesn't take long for us to realize that John is not schizophrenic but autistic, and that he's been drugged into a near trance, but the book isn't really about John.  It's about his sisters - resigned housewife-without-being-a-wife Ida, 40ish spinsters Winnifred and Ella, and wealthy widow Zorah who on her periodic visits is the only person who treats John as a sentient being.  During Kirsten's year with the Cosways, Winnifred becomes engaged to the local curate and Ella begins an affair with a loutish artist who's moved into the village.  It's a novel of small things which have major outcomes, and one in which the central events just couldn't happen in today's world of cell phones and internet research.  Miss Marple would enjoy The Minotaur - it's a book for students of human nature.