The opening scene is perfection. We meet the eponymous heroine of Diane Johnson’s latest novel, “Lorna Mott Comes Home,” as she rides in the back of a taxi, en route to the train station in Lyon.

Last summer, my husband had gone hiking with our two dogs when one of them — a year-old rescue who weighs in at over 50 pounds, can scale steep inclines like a mountain goat and has the speed and grace of an Olympic athlete — suddenly collapsed.

There are the rich and there are the very rich, and while the very rich exhibit varied demographic characteristics, the family at the center of Jenny Jackson’s sparkling debut novel, “Pineapple Street,” is of a highly specific sort: the pedigreed, never-touch-the-trust-fund-principal, tennis-playing, old-money-Brooklyn WASP.