ONE FIFTH AVENUE By Candace Bushnell Voice. 433 pp. $25.95 Rather than structuring her tale around a group of girlfriends as she did in her previous print-to-screen successes, "Sex and the City" and "Lipstick Jungle," chick-lit matriarch Candace Bushnell focuses in her new novel on a Manhattan landmark: a fabulous, towering, art deco co-op (real) and the intertwining stories of its posh residents (fictional). They range in age from a 13-year-old computer whiz to an 82-year-old gossip columnist. Don't be fooled by the age spread, though. At its ... (more)