A computer that writes haiku? Not surprising in a country where the emperor sponsors a yearly contest for haiku amateurs, of which he himself is one, and the mammoth circulation daily newspapers print them regularly. Haiku, like noisy noodle-slurping, is a fact of life in Japan, and thus visitors to the Sony building in downtown Tokyo could recently play with a machine programmed to arrange artistically selections of the popular haiku characters -- moon, snow, plum, cherry blossom, etc.

But poetry isn't all the Japanese like to write/read: there are perhaps twice an many bookstores in Japan as there are in the United States, and the book industry, if not quite thriving (it has some of the same problems that exist in America) keeps them filled. Says one publisher: "We can sell the books at the top of the list and at the bottom; it's the books in the middle that cause trouble." Non-fiction and how-to lead fiction in sales, but one thing different in Japan is the appearance of original fiction, in addition to haiku, in the daily papers. Asahi Shimbun, with a daily circulation of over 7 million, for example, has been running for nearly a year and a half a suspense serial by Seicho Matsumoto, Japan's "Agatha Christie" or grand old man of mystery.

Michio Mizuno, the culture and arts editor of Asahi, describes Meiso-chizu ("A Maze") as a story about political rivalry and blackmail. Such big-name authors as Matsumoto, he says, are fought over, with these unfolding yarns commanding prices of 15-16 million yen (approximately $64,000). Oddly, the paper itself approaches the writers with the basic plot ideas, and the writer takes it from there. "We don't know how it ends," Mizuno jokes, "but we hope it will finish." Book advertising runs on the front page of the paper regularly, and, in Asahi Shimbun, book reviews appear once during the week and on Sundays. Mitsutaka Sakata, Asachi's book review editor, believes the reviews he runs "have substantial impact" on book buyers because of his reputation for being very choosy in the books he assigns for review.

Such foreign celebrities such as Sean Connery, Paul Newman, Kirk Douglas and Marcello Mastroianni can be seen everywhere on billboards, endorsing Japanese products, and a stack of imported copies of Gordon W. Prange's At Dawn We Slept: The Untold Story of Pearl Harbor, of all things, is the most prominent display in one hotel bookshop. But foreign titles, though there are hundreds translated into Japanese every year, are not what lead the Japanese best-seller lists. Acutally, there isn't really an over-all industry best-seller list per se; rather, the bookstores each compile their own monthly statistics and the newspapers on Sunday will run a representative sampling of these. Sanseido is a century-old 14-branch chain with its flagship store a six-floor establishment at the heart of Tokyo's Kanda book district. Crammed with new books and magazines (it even has an optical department, so you can change your prescription if you've been browsing too strenuously) on all six floors, Sanseido's best-seller list is representative of general-interest retailers.

In fact, the only foreign book anywhere near a top-seller on a Sanseido March list is Entropy: A New World View by Jeremy Rifkin and Ted Howard, published in American by Viking in 1980. Other very successful titles include the current national sensation, Letters From Mr. Sagawa by Juro Kara, the pen-name of an author who's an avant-garde playwright and actor, as well as a novelist. Part of the book is real, a correspondence between the author and Issei Sagawa, a Japanese graduate student in Paris who in 1981 murdered a Dutch girl and turned her into sashimi. (This act of cannibalism has embarrassed both the Japanese and the French governments; the young man's father, on the other hand, knew just what to do -- he resigned his job in disgrace. Meanwhile, Mr. Sagawa remains incarcerated in France.) The rest of it is a fictionalized account of the gruesome killing and aftermath.

Winner this year of the Akutagawa Prize, a prestigious literary award, Letters From Mr. Sawawa has sold nearly a half-million copies within a fairly short time. Hardly in this league -- only 30,000 plus books sold -- Your Choice of Underwear Is All Wrong by Chiyoko Sugimoto is nonetheless another peculiarly Japanese best seller. A guide to improving your figure through foundation garments -- no exercise, no diet -- maybe it's not such a weird idea for a book, after all. Western women, however, have not been disguising their shapes with kimonos all these years, and that's certainly part of the Japanese female's problem, says Sugimoto, along with the poorly designed domestic bras and girdles.

Takashi Hirose's Why John Wayne Died is also a somewhat odd, or oddly titled, popular book at Sanseido and other stores. Not a film book, it does, though, blame the cancer deaths of Wayne, Steve McQueen, Gary Cooper and other cowboy stars on environmental carcinogens to which they were exposed when shooting movies down wind from the nuclear test sites in Utah. This book is selling especially well to college students and those involved in ecological and disarmament activities. Two other currently best-selling authors, both with previous hits to their credit, are Takenori Emoto, a handsome and articulate pitcher for the baseball team, the Hanshin Tigers, and Kenji Suzuki, a television newscaster who's a cross between Walter Cronkite, Alistair Cooke and Leo Buscaglia. Suzuki's books are about improving the relations between people and trying to break down some of the formality and inhibitions that characterize Japanese society; the latest is called To Care About Other People. Emoto's most recent book translates as How To Watch a Baseball Game More Efficiently.

As anyone who's visited Japan knows, English words can -- and do -- appear anywhere. They represnt a fashionable "otherness," and schoolchildren's pencil cases, for example, display a variety of bizarre, often incomprehensible, English phrases like "Rainbow time now" and "California move to." The distinguished American lexicographer Stuart B. Flexner is the adviser to The Shogakukan Dictionary of New English, which we noticed in a Maruzen book store, another chain over 100 years old with branches throughout Japan. What are some of the "30,000 new words" contained in this dictionary? "Linda Ronstadt," "kinky boot" and "two-way cable television," to name three.

Manga, however, is one Japanese word that any foreign visitor interested in books in Japan can't help learning. The manga are the illustrated pulps, or comics, that are read by laborers and businessmen alike, with some single comics selling as many as 2 1/2 million copies in one week. Says Frederik Schodt, in his forthcoming study, Manga! Manga! The World of Japanese Comics (Kodansha International), "Over 4.3 billion books and magazines were produced in Japan in 1980 . . . 27 percent of this total, or roughly 1.16 billion, were comics." There are humorous manga for rchildren and for adults, science fiction, sports, and pornographic manga and even, a new development, manga for adult women, perhaps for the same market as our Harlequins, since the name of one of them is Be in Love (another is Big Comic for Lady ).

One final thought: it will be interesting to learn if Hayakawa Publishing, which does more English and American writers in translation (from Dick Francis to Saul Bellow) than any other house, will have a success this time around with Herman Wouk's The Winds of War, the mini-series which began airing in late March on Japanese television. In the early '70s, when it originally came out, "we couldn't sell it in hardcover," comments Hiroshi Hayakawa, son of the company's founder, "and we had lots of returns out of our 10,000 copy printing." This time they're doing 35,000 and are going to offer giveaway books in TV ads, to the first 300 who write in. "Profit is the most important thing," says Hayakawa, "but we also owe it to the Japanese reader to make available books from English that may not make money for us."