Pain. Everyone experiences it, yet we have trouble talking about it and science has only recently begun to understand how it works. Pain: The Fifth Vital Sign is a groundbreaking inquiry into the nature, treatment, and definition of modern pain.

In the United States, there has been a recent campaign to treat pain as the fifth vital sign. Just as temperature, respiration, pulse, and blood pressure, the four traditional vital signs, must be charted, hospitals are now obliged to assess pain in their patients, too. If this indeed happens, it will be nothing less than groundbreaking—making pain far more visible.

But how has it come about that we spend $24 billion a year in North America on Tylenol, Advil, and the rest, and yet chronic pain is on the rise? Why is it that medicine can master intrauterine surgery but it can’t help people with bad backs or migraines? Pain is the number one reason why people go to the doctor’s office, and the number one reason they come away disappointed.

For a long time, pain has been a dark continent, both in the body and in our culture.

However, medicine is finally learning to evaluate pain as something more than a symptom—a main focus rather than a frustrating side issue for doctors. In the questing and narrative manner of an Oliver Sacks “neurological novel” or Sherwin Nuland’s inquiry into dying, Pain: The Fifth Vital Sign maps this largely unexplored territory through the stories of people who live with pain—from fibromyalgia to phantom limb pain—as well as the words of pioneers of pain research, and the professional experiences of doctors,scientists, and nurses.

Above all, Pain: The Fifth Vital Sign makes an elusive subject vivid and readable. We all know what pain is. Now it has a voice.