THE TUMOR THAT GREW inside Henrietta Lacks was unusual from its first appearance—"shiny and purple," growing rapidly, and "so delicate it bled at the slightest touch"—but nothing suggested that it would live forever. Although it caused Lacks' death in 1951, the HeLa cells it spawned began the first continuous human cell line cultivated in a lab. It's hard to overestimate HeLa's importance to modern medicine—it has played a crucial role in developing the polio vaccine, treatments for cancer, and drugs for influenza, hemophilia, and Parkinson's disease. The list goes on.

The Immortal Life of Henrietta Lacks is an achievement in its own right. The fact that Lacks was poor and black, the descendant of Virginian slaves and wife of a steel mill worker in Baltimore, is basically irrelevant to the science of the HeLa cells, but unshakable reality for those who survived her. The book is as much about HeLa's creation, uses, and commoditization as its emotional impact on Lacks' family, and the murky bioethics that intermediate. Skloot navigates both the technical and deeply personal sides of the HeLa story with clarity and care.

The Lackses didn't find out about HeLa until the 1970s, and the revelation was at once inspiring, confusing, and painful. In the decade-long research process for this book, Skloot became especially close to Henrietta's daughter Deborah, who sums up the conflict like this: "When I go to the doctor for my checkups, I always say my mother was HeLa. They get all excited.... But they don't never explain more than just sayin', 'Yeah, your mother was on the moon, she been in nuclear bombs, and made that polio vaccine.' I really don't know how she did all that, but I guess I'm glad she did, 'cause that mean she helpin' lots of people.... But I always have thought it was strange, if our mother cells done so much for medicine, how come her family can't afford to see no doctors?"

The second half of the book builds off the deepening relationship between Skloot and Deborah Lacks, as they research Lacks' genealogy and HeLa history in tandem. With every new chapter there's a gripping sense that "the answer" is soon to come, that Skloot will tell us whether the Lackses' rights were violated, and if they find justice. While she does finally provide the legal answer at the end, the one she gives through Deborah's process of coming to grips is far more meaningful and unusual.