Ever wondered why a book like Carl Sagan's Cosmos sold 900,000 copies in its 50 weeks on the Publishers Weekly best-seller list, but Rachel Carson's Silent Spring, which helped start the environmental movement, didn't? Cornell University professor Bruce Lewenstein gave a simple answermarketingon Monday at the annual meeting of the American Association for the Advancement of Science. "An author's style and personality and the presence he or she brings to a best-selling science book are generally the main factors in making it a bestseller," Lewenstein says. "The prominence of a science book author's personality has grown in the past 20 years."

What has grown, too, is the sheer number of science books that become bestsellers or win the Pulitzer Prize. Indeed, only two science books had won the Pulitzer before 1978, when Sagan and David C. Duncan co-authored the prize-winning Dragons of Eden. During the next 20 years, though, 12 other titlesamong them Douglas Hofstadter's Godel, Escher, Bach and Jared Diamond's Guns, Germs, and Steelwon the prestigious award. In general, Lewenstein notes that nonspecialist general readers are more likely to pick up bestsellers, whereas scientists or those with a close interest lean more toward influential titles, regardless of sales. See which ones below that you've read.