After years of biopsies, best-selling author Sarah Thornton made the difficult decision to have a double mastectomy. But, after her reconstructive surgery, she was perplexed: What had she lost? And gained? An experienced sleuth, she resolved to venture behind the scenes to uncover the social and cultural significance of breasts.

Riotous and galvanizing, Tits Up excavates the diverse truths of mammary glands from the strip club to the operating room, from the nation's oldest human milk bank to...