““Girlfriends’’ is a simple enough concept: it celebrates female relationships through a mix of anecdotes and catchy quotations about solidarity. Put out by a small publisher in the fall of 1995, it was not expected to be a hit. But in this world of broken marriages and far-flung family, ““Girlfriends’’ struck a deep chord. Women started buying six of the books at a time and mobbing the authors’ personal appearances. Fans began sending Traeder and Berry hundreds of letters a week with their own tales, and this year Oprah even dedicated her Valentine’s Day special to the girlfriends phenom. Now, after 12 weeks (and counting) on the best-seller list, Traeder and Berry are thrilled - but not surprised. Wherever they go, women testify to the primary role other women play in their lives. As one woman confided to them, ““I’ve been divorced three times, but my girlfriends have been with me for life.''

Berry and Traeder are hardly alone in recognizing such a need. Sentimental books about platonic female intimacy are all the rage in publishing these days. ““Sisters,’’ a photo-album-size paean to feminine familyhood, started the trend when it came out of nowhere to dominate the best-seller list last year. Industry giant Doubleday lured the book’s authors, Carol Saline and Sharon Wohlmuth, away from their small publishing firm, paying them $2 million for their second book, ““Mothers & Daughters.’’ Competition in the field is so fierce that the jilted publisher– Wohlmuth’s own brother-in-law, as it happens - put out a virtual look-alike entitled ““Daughters & Mothers.’’ (No one ever said relationships with male in-laws were so special.) Another ho t entry is ““The Mother-Daughter Book Club,’’ a how-to guide for parents searching for a televisionless way to bond with their kids. Traeder and Berry are even trying to cash in again with a follow-up, a fill-in-the-blanks album called ““The Girlfriends Keepsake Book.’’ Elaine Petrocelli, an independent bookstore owner, says what the books share is an understanding that ““women want, and have been looking for, a way to express their need for each other.''

Berry and Traeder got the idea for ““Girlfriends’’ a few years back when both found themselves in the throes of life crises. Traeder was miserable as a corporate lawyer, while Berry, recently robbed at gunpoint, was afraid to leave home. Both were single, and it was their gal pals who provided the emotional support that helped them move on. They wanted to create a book that would honor these ties by focusing on positive stories. They write, for example, about a group of women in Los Angeles who ha ve elaborate rituals for dealing with each other’s problems. Every time one breaks up with a boyfriend, the others gather at her house, turn off all the lights, and go from room to room with candles, tossing a bit of salt into each as a purification rite . Traeder and Berry also bring us the story of Donna, whose friends responded to news of her breast cancer by bringing her family meals every night for six months as she underwent chemotherapy.

But just as important to the book is what didn’t go into it, namely a strident, angry tone. In person, as in print, the women leaven their earnestness with playful banter. When Traeder asks her coauthor to recall the year of a certain radio appeara nce, Berry answers, ““Well, when was the last time you were a blonde?’’ They carefully avoid the controversial (lesbianism) or the off-putting (male-bashing). And they say little about the book’s obvious subtext - that men have failed to be responsible p artners. But the opposite sex may not be spared much longer, and female friendship may get some edge. Traeder and Berry are working on a sequel: ““Girlfriends Talk About Men.''