IN ONE of his last books, Roland Barthes imagined a "faraway" country, a "fictive nation" with distinctive features that "deliberately form a system." Barthes called his system Japan. That was a French semiologist's approach to Japan, his curious way of understanding an impossibly difficult language and the country's myriad mysteries: sumo wrestling, pachinko machines, homes without real addresses, puppet theater, calligraphy, even the Japanese eyelid. Barthes' The Empire of Signs is one of the best books on Japan by a Westerner largely because of the observer's idiosyncratic approach. "There is nothing to grasp," Barthes concluded, and he ended his brief study delighted but still mystified by his "fictive" nation, his new Garabagne and Lilliput.

John David Morley, an Englishman who spent three years studying and working in Japan, contrives a less satisfying, if equally idiosyncratic, approach to Japan. He, too, means to confront its overwhelming strangeness. He wants to know why, in a country so accustomed to the sight of Americans and Europeans, girls giggle at Westerners in the street, why Japanese conversation is such a treacherous field of ambiguity and ritual, why, in a city as crowded and dusty as Tokyo, women wear white socks with their sandals and subway station masters wear white gloves.

For three months, Morley writes, he lived apart from the Japanese. He studied, he observed, he took strolls in the neighborhoods of Tokyo, he improved his Japanese to the point of academic fluency -- in short, he did everything a seriously inquisitive visitor should do. But he kept his distance. That is until one winter night in a bar when he met a man named Ichimonji. With Ichimonji as his guide, Morley began a tour of the mizu-shobai or "water trade," Japan's countless and various taverns, its world of geishas, Turkish baths, strippers, prostitutes, "love hotels," and "pink cabarets." Tokyo can be a nighttown of harlots high and low, and Morley, aided by his facility with the language, broke through many of the barriers erected for any visitor to Japan. It was a revealing binge.

Morley writes that after his first night out he "woke up to find that overnight he had arrived in Japan." He had discovered his memoir's idiosyncracy, his vehicle to a "faraway" place: the "water trade."

"Celibate, studious, his intellect committed but his heart undecided, he might have stood wavering for a bit longer had Ichimonji not seized him by the scruff of the neck and pitched him into the magic circle where words and sentences became palpable events, a clamour of voices, faces and sensations, no longer a dumbshow but a glittering stage where the actors walked and talked, abruptly waking him out of his dream."

The Japanese, as Morley discovered, take great pride in what they believe to be the uniqueness and impenetrability of their culture. They are stunned when a Westerner enjoys a snack of eel and sake. Some are even disappointed when an outsider, a gaijin, is able to speak or write Japanese. "You would never understand" is the implicit message from the Japanese to Westerners.

The pleasure in Morley's book is that he so often does understand things Japanese and lets us in on the secrets. He explains the system of aizuchi, a technique of conversation that promotes the speech of others using one-syllable bursts of attentiveness: the Japanese equivalent of "yes!," "I see!," "you don't say!" He is very good on the Japanese obsession with "appropriateness," the rigid distinctions between pleasure and work, the reasons why uniforms are such an integral part of Japanese life. He explains with sympathy and attention the concept of the small group, the uchi, discovering how the lack of distinct rooms and central heating in a traditional Japanese house helps make family life close and relaxed. Above all, Morley's knowledge of the "water trade" is encyclopedic and often provides a witty, revealing way of understanding marriage and relations between men and women in modern Japan.

PICTURES FROM THE WATER TRADE, though, is a potentially brilliant book marred by mistaken strategy. For one reason or another, Morley decided to write about himself in the third person using the name "Boon," an idiosyncracy that adds little but confusion and distance.

"Boon" is Morley's, and the reader's, bane. Boon is one of the most reticent figures in the book, a caricature at times of the national personality he proposes to describe. Too much is left unsaid. We know where Boon is from, that he lives on a grant from the Japanese ministry of education and various teaching jobs, that he came to Japan because "he had once seen a Japanese walk across a stage in a way that deeply moved him." That's about all. We never get a sense of how things Japanese affect this Westerner, as we do in Brad Leithauser's fine new novel about an American in Japan, Equal Distance.

When he gets around to having an affair with the inevitably "mysterious" Japanese girl, Mariko, we've lost much of our interest in "Boon" as a character; he is only a clumsy device to teach us about Japan.

What we learn from Morley about the "empire of signs" is welcome and a delight. How we learn it is less so. When Morley tells us near the end of Pictures from the Water Trade that he began to act Japanese, bowing during telephone conversations, it's hard to believe him or care. "Boon" stands in the way.