When Farrar, Straus and Giroux announced a 1.6 million-copy first printing of Tom Wolfe's raunchy college novel, I Am Charlotte Simmons, many assumed it would mimic the success of his previous zeitgeist-capturing best-sellers, 1987's The Bonfire of the Vanities and 1998's A Man in Full. But as of Feb. 13, Charlotte had sold roughly 250,000 copies, according to Nielsen BookSoan, which tracks about 70 percent of U.S. sales at more than 7,000 outlets. (Many stores now sell Wolfe's book at half price.) Why the falloff? ''It's been commonplace that, with one or two exceptions, the marketplace for literary fiction has not been as strong as it was just a couple of years back,'' says FSG's Jeff Seroy, adding the publisher is satisfied with Wolfe's numbers. BookScan reports even grimmer sales for two other fall 2004 titles acquired with much fanfare. The Soul of a Butterfly, a spiritual memoir by Muhammad Ali with daughter Hana Yasmeen Ali, has sold just 22,000 copies; the publisher had no comment. And Pope John Paul II's Rise, Let Us Be on Our Way has moved 39,000 (his 1994 memoir, Crossing the Threshold of Hope, sold 500,000 copies in its first few days). Says a disappointed Todd Doughty of Warner, ''We did outreach with the religious market, but it just wasn't what we had hoped.''