Emily Rapp is a remarkable woman. Despite losing her left leg as a child to a congenital defect, she proceeded to become an accomplished skier, scholar, and adventurer. But the soldier-on toughness that helped Rapp live a rich life deprives her self-portrait of any depth. Her memoir certainly hints at psychological pain — an eating disorder, debilitating panic attacks — but they are mentioned and then dispatched so swiftly that Poster Child becomes a frustrating laundry list of the logistics of walking with and caring for a prosthetic leg. Rapp’s accomplishments certainly make her worthy of admiration, but a sense of just how she’s achieved them never makes it to the page.