Gender isn't what it used to be. Categories are collapsing. What was deviant for baby boomers has become mainstream for their offspring: like the coed who realizes she's bisexual but, after a period of adjustment, shrugs her shoulders and gets on with her otherwise mundane life. Gender as we once understood it is over, and gender-bending is the new beat. Men sport ponytails and earrings and teach nursery school; women flaunt tatoos and biceps and...