More in the instant personality-profile department: oldest child, youngest child, middle child; boy, girl; and the various combinations and permutations thereof. These are written in the second person and tend to imitate the cadence of horoscopes (the only child, or ""singleton,"" exhibits ""your imaginative and innovative approaches to many events--at home or in your business and social life""). There's something in this for nearly everyone: girl singletons ""are probably the most independent of all the people in this book""; youngest boys have a very high degree of success (though they either choose their life's work young or hop from job to job throughout life). The shortest straw seems to have gone to the middies--unless age gaps leave them in one definite camp or the other--since they generally feel completely left out and acquire whatever they can ""in the face of adversity and confusion."" The authors--psychologists who draw their composites from readings, private practice, and personal observation--manage to branch off enough to consider two-sibling combinations (older brother of younger sister, older brother of younger brother, etc.); but clearly they don't feel they've exhausted the possibilities. ""If we had the time, money, and research facilities for studying large families,"" they cluck, "". . . We could then talk about. . . 'the middle girl with two sisters and two brothers.'"" Piffle.