Alexander Popper can't stop remembering. Four years old when his father tossed him into Lake Michigan, he was told, Sink or swim, kid. In his mind, he's still bobbing in that frigid water. The rest of this novel's vivid cast of characters also struggle to remain afloat: Popper's mother, stymied by an unhappy marriage, seeks solace in the relentless energy of Chicago; his brother, Leo, shadow boss of the family, retreats into books; paternal grandparents,...