"More than thirty years ago a pioneering young adult librarian named Margaret A. Edwards protested that 'many adults seem to think that if sex is not mentioned to adolescents, it will go away.' "As succeeding decades have demonstrated, silence is no arbiter of behavior. Not only has sex not gone away, it has become a quintessential -- perhaps even obligatory? -- rite of passage for adolescents." So writes Michael Cart in his foreword to "Love and...