NONFICTION - Sept. 1, 1996

YAKUZA DIARY: Doing Time in the Japanese Underworld by Christopher Seymour (Atlantic Monthly: $22; 212 pp.) Most people know only the flashiest, most publicized facts about the Yakuza, or Japanese gangsters. They perm their hair, cut off their fingers and get full body tattoos. After spending three years in Japan interviewing various shady characters, journalist Christopher Seymour put together “Yakuza Diary,” a highly detailed, personal and subjective look at the Japanese underworld.

“Yakuza Diary” is one of those books with a thick demarcation line between the interesting and slightly tedious sections. The deciding factor is always the same--Seymour’s point of view. The more his own brand of cheerful self-interest comes into play, the better the writing. Here is Seymour dealing with an immigration official. “I was seated in front of the worst kind of Japanese bureaucrat, a fat one. He was fat because he never stands up to bow . . . much to my horror, I had no idea how to play him. I was suffering the con man’s equivalent of writer’s block.” Seen through that sort of lens, the Yakuza are unfailingly compelling. However, the moment Seymour withdraws his sharp, slightly enigmatic personality, the book becomes a lot less fun to read.