To define "migraine, " suggests Oliver Sacks, one must embrace the dizzying variety of experiences of its sufferers. For some, the affliction features of a headache of monumental proportions. For others, there is no pain at all. Some attacks are triggered by weather, some intense light. Still others consist of intense light -- hallucinatory displays of dazzling loops, stars, and geometrics.

"Migraine" is Sacks's brilliant examination of a debilitating ailment and the profound implications of neurological illness. Synthesizing his patients' case histories with 2,000 years of human research into the problem, he casts the migraine as exemplar of our psychological transparency, a complex biological response to external factors. Here is a classic meditation on the nature of health and malady, on the unity of mind and body. Here, too, is Sacks's discovery of how the migraine shows us, through hallucinatory displays, the elemental activity of the cerebral cortex -- and potentially, the self-organizing patterns of Nature itself. Enormously compelling, compassionate, and profound, Migraine offers comfort for sufferers -- and insight to all.