It's been a long time since I read anything by William Trevor (30 years?) and so I wasn't sure what to expect from this novel. Yes, it was overly long for the subject matter - as another reviewer has suggested, it might have made a more efficient "long short story". Yes, it was terribly nostalgic and very old fashioned, but I enjoyed it nevertheless. I liked the intensity of it, the innocence of a long-gone simple rural Ireland (the young wife and her older husband), simple yet at the same time complex with its newly emerging property-based class system replacing - and aping - the system of the British, Anglo-Irish and Protestants. What is known now about clerical abuse and the structures that enabled it to thrive belie the innocence of the time - I wonder if Trevor had this in mind. For some reason it "Love and Summer" reminded me of "Ryan's Daughter" - the repressed sexuality of the young wife, and the tenderness and kindness of the older husband.
The Connulty twins and the parent to whom each was respectively attached represent two sides of the one coin of the allegedly pre-materialism days that people apparently yearn for: the cold mother who invested more in her son and the father who ultimately stood by his daughter in her time of need. The young lover's decaying house and his besotted artistic parents bring to mind Yeats' "romantic Ireland" being "dead and gone, ... with O'Leary in the grave." Romanticism doesn't feed you, despite its many attractions.
I did enjoy this book, but it rightly didn't win the Booker.