Whether Orion ought to be feet- or head-up in the night sky depends on the hemisphere. When Stan, a 23-year-old student from South Australia, rides his bike through the Rocky Mountains, he marvels that the constellation is upside down.

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.

“It seemed to be one of life’s wonders,” observes Sherwyn Sexton, the not wholly unlikable cad at the center of Fay Weldon’s lively if sometimes frustrating new novel, “Before the War,” “that nothing happens and nothing happens and all of a sudden everything happens.”