I worked in bookstores for 8 years. The most popular genres for women were actually #1 mainstream, dramatic literature (e.g. Kite Runner, Middlesex, Life of Pi, etc.) and #2 Thrillers. I would say "chick-lit" (Confessions of a Shopaholic, Girls Guide to Hunting and Fishing, etc.) came in third. Of course, it varied a lot from community to community. When I worked in a blue-collar town we sold a lot of Romance, whereas in a wealthy town with an older population we sold almost none.