Jean Kwok can keep a secret. For three years in her twenties, the bestselling author (“Girl in Translation”) and Harvard grad worked as an award-winning ballroom dancer and instructor for Fred Astaire Dance Studios in New York City. But despite her achievements, Kwok never quite got around to telling her traditional Chinese family about her life in sequins – until now. In her new novel, “Mambo in Chinatown,” Kwok revisits those secretive worlds through Charlie Wong, a self-described wallflower who finds love, confidence and acceptance on the dance floor.