The surprise literary hit of the summer is the hefty authorized edition of "The 9/11 Commission Report: Final Report of the National Commission on Terrorist Attacks Upon the United States." Tomorrow it will be No. 1 on the nonfiction paperback bestseller lists of The Washington Post and the New York Times.

More than half of the 600,000-copy first printing has sold so far, according to Nielsen BookScan. The publisher, W.W. Norton, is printing another 200,000 in anticipation of continued sales well into the fall.

Norton's president, Drake McFeely, says he finally believes his company will make a profit on the venture. "But we can't tell," he adds, "until the dust has settled -- in six months or so." The company will not know how many books it has sold until booksellers have returned unsold stock.

Following on the heels of Norton's $10, 567-page book, St. Martin's Press has published a less expensive version that promises "reporting and analysis by the New York Times." The 768-page book sells for $6.99.

A free version of the report is available at the Government Printing Office Web site. And a printed edition is also offered through the GPO for $13.25 (with shipping; without, it's $8.50).

Norton got a head start on the competition when it was selected by the commission in May as the authorized publisher. Al Felzenberg, a spokesman for the commission, says Norton was chosen over several other publishers because it promised to distribute the book quickly at a reasonable price.

According to the commission's contract with Norton -- obtained by The Washington Post -- the publisher also agreed to print at least 200,000 copies and to try to prevent the report from being leaked ahead of the commission's unveiling at a July 22 news conference. The contract also stipulated that Norton would publish a hardcover version, that no royalties or other payments would go to the commission and that the price would remain $10 or less for at least 12 months.

The commission was keen, Felzenberg says, "on getting it out to the American people so they were part of an informed debate quickly."

He adds, "The copyright belongs to the American people." Any publisher can produce a version.

McFeely says Norton took a financial risk, not knowing how well the book would sell and that his company will donate "any extraordinary profits" to an appropriate charity or charities.

Stuart Applebaum, a spokesman for rival publisher Random House, says his company is comfortable with the arrangement. In an e-mail, he writes, "Aside from wistfully wishing that every commercially successful book was ours, we are living without second guessing the Commission's choice of its report's publisher and are glad the book is being widely purchased and hopefully just as widely read."

Staff writer Dan Eggen contributed to this report.