Melanie Thernstrom has a congenital neck-and-shoulder problem that has kept her in constant pain for the past 10 years. Pain is something you can’t stop thinking about, and Thernstrom is the kind of person who can’t stop thinking anyway. The fruit of her misery is “The Pain Chronicles: Cures, Myths, Mysteries, Prayers, Diaries, Brain Scans, Healing and the Science of Suffering” (Farrar, Straus and Giroux, $27).

As that subtitle suggests, it’s a big, discursive book. Chronic pain affects 70 million Americans. They all have a story. Thernstrom has looked into pain from every angle, so she nestles her own inside a tangle of history, science, religion and reflection.

Sometimes she’s incredulous: “Although it is difficult to believe, the invention of surgical anesthesia (through the inhalation of ether gas) by an American dentist in the mid-19th century was controversial at the time. Many agreed with the president of the American Dental Association, who declared, ‘I am against these satanic agencies which prevent men from going through what God intended them to go through.'”

Her accounts of surgery before anesthesia are fascinating and appalling. So are her descriptions of people who have subjected themselves to pain for nonmedical reasons — Christian saints and Jewish martyrs, with their hair-raising stories, as well as believers who still put themselves through ordeals out of religious zeal.

She travels to Malaysia to witness the Hindu festival of Thaipusam, during which some pilgrims pierce their tongues or their cheeks; others hoist heavy altars onto their shoulders attached by hooks to their chests, or drag ceremonial carts by ropes hooked into their backs.

What’s most striking about these zealots isn’t the cheerfulness with which they submit to being mutilated but their apparent lack of suffering. This is Thernstrom’s real motive: She wants to understand how they overcome their pain so that she can learn to control her own.

The answer lies somewhere in the brain. A neurophysiologist tells her, “Everyone is born with a system designed to turn off pain,” which is what happens, for example, after a serious injury: The brain first counters the pain impulses and later exaggerates them, an evolutionary refinement enabling flight when the shark bites off your arm and enforcing rest later on.

The neurophysiologist continues, “There isn’t an obvious mechanism to turn off other diseases, like Parkinson’s. With pain, the system is there, but we don’t have control over the dial.”

The last part of the book is about controlling the dial. New brain-scan technology allowing subjects to observe and modify their own mental activity offers great promise. But as with cancer research, the progress is heartening, the cure elusive.

In the case of pain — a hugely complex form of consciousness involving many areas of the brain — it may never arrive, an eventuality Thernstrom understands all too well. As much as she wants to be free from pain, as positive as she strives to make herself, she isn’t delusional. And so her book is the sum of myriad small observations and discoveries and epiphanies, but no revelations. There are no magic words to lift the spell.