>> announcer: from the global resources of abc news, with terry moran, cynthia mcfadden and bill weir in new york city, this is "nightline," january 26th, 2011. >> and good evening from a snowy new york. we begin tonight with parenting. dr. spock baby and child care book has sold more than 50 million copies since its 1946 publication. but now, a new kind of parenting book is flying off the shelves, and the author we speak with tonight has critics roaring about her sharp-clawed advice. here's juju chang to talk with the author, and with moms of a few different stripes. >> reporter: pa...