Except for the very occasional appearance of Albert Ellis or Margaret Mead, this is just Cosmopolitan girl talk about the 15 million who've found ""where it's at"" together in the big cities. . . how they live together, just girls, just boys, singles, or doubles couples, on up to the minicommune; how they feel about having a homely roommate or pot or sex; how they find a place to live with someone else (there are agencies); and how they bookkeep or break up. After all, this is ""very like a marriage, minus the vows"" although it's hard to think of it this way. Just girl-to-girl carpeted confidences of Bitsy and Bonnie and Lannie and Winnie or Dottie -- ""We have very groovy sex, she says, pulling on a 100 mm. cigarette.