It’s the book to beat this Christmas.Michael Crichton’s “Prey,” a novel about a swarm of murderous particles unleashed by a biotech lab in Nevada, descended like a plague of insects on bookstores little more than a week ago. Rival publishers are already gunning for it, hoping Crichton will become the 2002 fall bookselling season’s Jack Welch, whose memoir, “Jack: Straight From the Gut,” floundered last year, despite massive hype and a book advance that’s one of the highest on record. Reports have surfaced in the New York Times and the Washington Post that sales of “Prey” are flagging as part of an industry-wide decline in blockbuster fiction sales. The book-buying public has recently turned a cold shoulder to new books by brand-name authors like Tom Clancy and Stephen King. There are early signs that holiday shoppers are looking for quirkier fare, like Alice Sebold’s first novel, “The Lovely Bones,” Yann Martel’s Booker Prize-winner “The Life of Pi,” and Tuesday’s Amazon.com No. 1 bestseller, “The Sopranos Family Cookbook.” But “Prey,” which currently sits comfortably astride the fiction bestseller list, is selling faster than any of those titles, and HarperCollins executives resent the allegations that the book is under-performing. HarperCollins says sales of “Prey” are robust, that it’s selling as much as 25% faster than hardcover sales of Crichton’s 1999 novel, “Timeline.” That would put it on track to sell well over a million copies in hardcover. But as publishers struggle to gauge customer demand in a stagnant book economy, HarperCollins has reason to feel defensive. In 2001, Crichton received one of the highest book advances in history – some $40 million for “Prey” and one other book – to leave Knopf, his publisher of nearly three decades, and join the HarperCollins fold. The deal may prove valuable to HarperCollins even if “Prey” doesn’t generate overnight profits. But paying an author a $20 million book advance — much like a $30 million salary to a box-office star — doesn’t leave much room for profits, and it’s no surprise that other publishers tend to resent it. Crichton’s “Jurassic Park” is one of the most profitable of media properties, but it was the Steven Spielberg movie that made the book a huge international franchise, launching theme park rides and scores of merchandise spin-offs. HarperCollins’ parent company, News Corp., hopes “Prey” and the next book have a second life onscreen. Crichton and his publisher gave Fox a first-look at “Prey,” and they took the book off the market with a $5 million pre-emptive bid. But HarperCollins bought “Prey” sight unseen, and the topic might not prove quite as cinematic as marauding dinosaurs. “When you look at ‘Jurassic Park,’ that is a natural product for diversification and licensing,” says Trident Media Group head Robert Gottlieb. “But not every bestselling book is a natural franchisable property.” Like movie studios reliant on ancillary markets and homevideo sales to recoup on big-budget movies, publishers tend to derive their biggest profits from backlist books with enduring shelf lives. HarperCollins, which is negotiating to pick up a large swath of Crichton’s backlist, clearly expects “Prey” will have a long shelf life. By laying claim to the top-selling book of the season, HarperCollins has also planted a flag in the market, further establishing itself as a publisher of high-caliber commercial fiction, and providing greater leverage in the market for other HarperCollins titles. HarperCollins CEO Jane Friedman told Variety last year, the book serves, in part, as a market wedge. “Sales reps love the idea of walking into a bookstore and saying, ‘We have the new Michael Crichton,’ ” Friedman said at the time.