Amazon.com Product Description (ISBN 0099466872, Paperback)

Scintillating, elegant, darkly comic, The Key is the story of a dying marriage, told in the form of parallel diaries. After nearly thirty years of marriage, a dried-up, middle-aged professor frenziedly strives for new heights of carnal pleasure with his repressed, dissatisfied wife, resorting to stimulants galore for her: brandy, a handsome young lover. During the day, they record their adventures of the previous night. When they begin to suspect each other of peeping into their respective diaries, it becomes unclear whether each spouse's confessions might not be intended for the other's eyes.

Translated from the Japanese by Howard Hibbett.