Adulthood, which once seemed an uneventful, predictable time of life, has more recently come to seem problematic and mysterious."" Uneventful to social scientists, maybe, hooked in recent years on adolescence and old age; but the occasional reference here to Jane Austen or Matthew Arnold suggests that literary folk have been on to it all along--and still have more interesting things to say than do these sociologists, psychologists, and psychoanalysts. The major problem: too little theory. Thus while Neil Smelser argues for placing work and love in the study of adulthood (rather than the sociology of occupations or of the family), only co-editor Erikson's (Childhood and Society) theory of the life cycle serves to guide debate, which logically divides into those like Daniel Levinson (The Season's of a Man's Life) who see predictable life stages and those like Marjorie Fiske (""Changing Hierarchies of Commitment"") who don't. A second problem: rediscovering the obvious. Leonard Pearlin (""Life Strains and Psychological Distress"") tells us that exposure to stress varies with individuals' social characteristics and by setting. Some people like retirement, some don't. Melvin Kohn (""Job Complexity and Adult Personality"") discovers that ""the structure of the environment has an important effect on cognitive development,"" that well into the adult years ""intellectual flexibility continues to be responsive to experience."" And, finally, Ann Swidler (""Love and Adulthood in American Culture"") sees ""new frontiers of the quest for identity"" appearing in the emerging emphasis on communication and understanding above permanence and commitment. The few perceptive notes sounded (Janet Giele's discussion of adulthood as the transcendence of age and sex categories, as allowing increasing ""crossovers"" and freedom from age- and sex-typed expectations) can scarce be heard above the jargon and pat formulations. A pretty tame frontier, if it's that.