Westover’s extraordinary memoir is an act of courage and self-invention. The youngest of seven children, she grew up in Idaho, in a survivalist family who lived so far off the grid that she lacked even a birth certificate and did not attend school until she went to college. Getting in wasn’t obvious: At home, reading meant studying the Bible and the Book of Mormon, and much of her childhood was spent helping her mother, an unlicensed midwife, and her father, a paranoid man who maintained a scrap-metal junkyard. In recounting her upbringing and her triumph over it — she would earn a Ph.D. in history at Cambridge — Westover took great risks and alienated family members. The reward is a book that testifies to an irrepressible thirst to learn.