Imagine a vaccine that could cure cancer. As this book reports, that possibility may not be far off. Cancer treatment has long relied on “cut, burn, and poison” methods: surgery, which science journalist Graeber (The Good Nurse: A True Story of Medicine, Madness, and Murder, 2013) notes has been with us for thousands of years, coupled with the more modern radiation therapy and chemotherapy. Immunotherapy leverages the body’s natural defense systems, made up of hundreds of millions of cells that are constantly “searching [for] and destroying the invaders that make us sick and the body cells that have become infected, mutated, or defective”—all of which describe cancer. Immunotherapy, in short, unlocks the natural-born cancer killer within, which is no easy task, inasmuch as a hallmark of cancer is its ability to lurk within the body undetected until, at least of old, it is too late. As the author chronicles, scientists have yet to completely understand the workings of the T cell “as the serial-killing attacker of foreign cells,” but they have figured out what switches that cell on: a system of responses that are “something like how multiple keys are required to unlock a nuclear button or to open a safe deposit box.” This helps moderate a constant danger that the immune system responses can sometimes lead to autoimmune diseases, where the cells lock onto the wrong thing; thus the “many redundancies and fail-safe feedback loops built into the immune response.” Enough has been learned that previously discarded immunotherapies are being studied to determine whether they would work “with the brakes off,” after having been paired with a “checkpoint inhibitor.” Graeber reports that immunology researchers are promising more soon—more drugs, more fast-tracking to get therapies into hospitals, more “biomarkers to better describe cancer with molecular specificity." Though sometimes clumsily written, the book offers hope for more effective treatments in the near future. A readable survey of the emerging field of immunotherapy in cancer treatment.