The author of the well-aimed You Are What You Eat (1977) and Fat Free (1975) branches out in a general advice book covering everything from acne and braces to VD. Chapter headings--""Am I a Sex Maniac?"". . . ""Am I Going Crazy?"". . . ""I Can't Sleep""--indicate the familiar nature of the contents. Realistically, Gilbert suggests alternative food plans and exercise programs for those who don't go for sports or gym workouts or for the conventional ""Three Squares."" On more highly charged issues, her approach is cautionary: drugs, alcohol, and tobacco are treated in a chapter titled ""Self Abuse."" (And ""people who say that pot is a safe and easy high are just stringing you along. Nobody knows for sure."") She notes that ""our society in general disapproves of intercourse between teenagers and this is one major drawback of the activity,"" and it's clear that she doesn't feel comfortable with the idea either--though she does recommend contraceptives to those who are sexually active. Without any shift in stylistic gears from one chapter to the next, Gilbert is really addressing the concerns of people at vastly different levels of maturity and consciousness (those curious about the changes of puberty are unlikely to need contraceptive information)--and this is one major drawback of all such broad advice books for teens. But Gilbert is better than most at sounding easy-going as she lays it on you, and readers at the younger, less sophisticated end of her range might extract some usable tips on a variety of common conditions. And surely the upbeat title and sunny cover will attract.