A profile of American Jewry in a gallery of portraits: Roger Kahn focuses on ""the amazing three per cent"" in the promised land, which is easier to contemplate than to live in. He writes of rabbis and writers, bar mitzvahs and businessmen, Jews in the East, Midwest and Far West. . . all manner of men in all manner of places. He witnesses them confronting their Jewishness and ponders the insoluble question of definition (""Was Trotsky, the atheist, Jewish? Is Barry Goldwater? Was Jesus Christ?""). His approach is experiential: a reconstruction of a super Bar Mitzvah, of the life of a doctor in a Southern town, a teacher in Harlem, an elderly rabbi in a mining community, a Hollywood agent reaching for God. It is not sentimental or even soulful: the life of the Jew has a hard edge of pragmatism and religion is not the half of it. The passionate people, whose worries are ordinary but whose kind of worrying is not, emerge in their likenesses and variances in the strong light of realism barely leavened by a constrained sympathy.