<p>Since fashions have been going retro -- from hip-huggers and halter tops to the recent '60s nostalgia hit ``Down With Love'' -- perhaps it was inevitable that ``Sex and the Single Girl'' would make a big comeback this summer. Barricade Books has dusted off Helen Gurley Brown's 1962 bestseller, given it a hot-pink cover and marketed it as ``A Cult Classic.''</p>