After losing her mother to cancer and spiraling into drug addiction, the young Cheryl Strayed decided on an impulse to hike the Pacific Crest Trail, a challenge she hoped would distract her from the wreck her life had become. Lighting out for the territory is the quintessential stuff of American literature; Strayed, who was such an amateur that she didn’t even try on her boots before hitting the trail, breaks down her body and builds it back up as she travels from California to Oregon and from bewildered grief to battle-worn resilience. Her touching memoir, which benefits from nearly two decades of hindsight, gains power from its unflinching portrayal of the hard parts — not the days on the trail, though they hurt too, but the memories of her mother’s life and death.