Carrie Sun used to be on the side of Big Money. Her memoir, Private Equity (Penguin Press, $29), describes her disillusioning tenure as an assistant to Boone Prescott, the founder of a hedge fund called Carbon. (These are both pseudonyms, and good ones; Boone’s name is so slick with patrician unctuousness that it wants to be whispered more than spoken.) At first, reading Sun’s dedication—for “all those who have the courage to quit”—I thought she might be a fox in the most deluxe of henhouses: a closet socialist who’d gaslight her boss into submission, fit him with a shock…