Check out this week's new hardcover and mass market fiction top sellers—there are five new titles in hardcover, seven in mass market (six of them among the top 10) and even a newcomer to the trade paperback list. Shelf life for fiction hardcover and mass market titles continues to get shorter. With all these new titles, there are only four fiction books that have been on the list a month or more; only two have a double-digit tenure. On the mass market side, six books have been on the list more than a month, with one—Dr. Atkins' New Diet Revolution—enjoying a very unusual three-digit tenure (271 weeks). Contrast this with the performance of hardcover nonfiction titles. There are two newcomers and three other books with four weeks or less on the charts; seven of our bestsellers have been on the charts for three or more months. Longevity is also apparent among trade paperbacks; here, about half of the list has had double-digit runs.