Could the biggest sensation of last year be one of the underperformers of this one?

Bill Clinton's My Life had the hugest hardcover nonfiction opening in history a year ago, as a reported two million people were willing to buy a book that carried a list price of $35. That resulted in publisher revenues larger than the total annual sales of most small publishers.

But so far, in the three weeks since the publication of the trade paperback and volume 1 of the mass market, the title has performed less impressively. Nielsen BookScan indicates total sales of about 35,000 copies—21,000 for the trade paperback and 14,000 for the mass market (called The Early Years; the second volume, The Presidential Years, is due out at the end of the month).

The number is substantial by some standards, but the bar is set high for one of the most successful books in history. The sell-through rate is not terribly encouraging: The company has averaged sales of 7,000 trade paperback copies per week on an announced print-run of 250,000, and about 5,000 copies per week on an announced mass market run of 500,000. (The sales figures should be considered in light of the fact that BookScan generally accounts for about 70% of sales.)

Booksellers say, perhaps because of a modest publicity campaign, that customer interest has been lukewarm. Susan Taylor, adult book buyer at Wellesley Booksmith, called the paperback a "big shrug." For Carol Stoltz, a buyer and co-owner of Porter Square Books in Cambridge, Mass., copies serve as "shelf decorations."

Asked about the book's sales, Knopf/Vintage spokesperson Paul Bogaards said, "We're pleased with the numbers in all sales channels, as well as the bestseller positioning." (The book hits at #5 on the current New York Timespaperback list.) And a BookScan official noted that some of the book's sales likely happen in food and drug stores, which are not covered by the service.

Still, the Clinton figures highlight a hidden trap for publishers of big-release books: paperback sales. Where most houses determine reprint runs based on the success of earlier editions, the model may not apply to blockbuster, event-driven books. In this case, Knopf may have done such a good job selling the hardcover that there aren't many people left to buy the paperback. (Other factors, like the elegance of a hardcover presidential memoir and the book's status as a statement in an election year, may of course have also played a role in the strength of the hardcover over the paperback.)

But Knopf/Vintage may end up fine. Bogaards says the model is the Hillary book, where Bill is off, but not terribly off, the pace. The paperback Living History sold several thousand more than My Life in the two books' first week out—and ended up selling between two and three hundred thousand copies.