Harry Potter and the Half-Blood Prince averaged better than 250,000 copies sold per hour, more than the vast majority of books sell in a lifetime.
"This is a cause for celebration, not just for Scholastic, but for book lovers everywhere," said Lisa Holton, president of Scholastic Children's Books, author J K Rowling's US publisher.
Sales for the sixth instalment of Rowling's fantasy series easily outpaced those for Potter V - Harry Potter and the Order of the Phoenix - which came out in 2003 and sold 5 million copies in the first 24 hours.
Acknowledging that some stores quickly ran out of books two years ago, Scholastic has already increased the print run for Half-Blood Prince from 10.8 million copies to 13.5 million.
The Scholastic numbers are for the United States only. Sales figures from Britain are expected on Monday.
Fans and critics alike have given
Anticipated from the moment fans finished Potter V, the new book has been available virtually everywhere, from price clubs and supermarkets to the Scholastic website.
Holton said on Sunday that a big factor in the new sales record was a six-fold increase in the number of Potter bookstore parties, from 800 to 5000, with superstores as well as independent retailers dramatically increasing their participation.
Even allowing for deep discounts on the $29.99 release, Half-Blood Prince still easily generated more than $100 million in revenue in the first 24 hours.
It's not only the richest opening in publishing history, but tops the combined estimated take for the weekend's top two movies, Charlie and the Chocolate Factory and The Wedding Crashers.
"When a book beats out movies, we're in great shape," Holton said.
The book's takings beat the two
top US films over the weekend
Paul Dergarabedian, president of box-office tracker Exhibitor Relations, said he did not believe that Potter pulled kids away from Charlie and the Chocolate Factory, which starred Johnny Depp as the reclusive candy king Willy Wonka.
"With a $55 million opening, it's hard to say anything had a negative effect on the movie's performance," Dergarabedian said on Sunday.
Unlike most blockbusters, Harry and the Half-Blood Prince is also a hit with critics, getting rave reviews from The New York Times, the Seattle Times, The Associated Press and others.
Many found it Rowling's deepest, most accomplished work, with a tragic conclusion that left even reviewers in tears.
A dissenting opinion came from the San Francisco Chronicle, where David Kipen observed of the 600-plus page novel: "A major character dies by the end of the latest Harry Potter book; readers who bore easily may feel a bit done in themselves.
"It's not that Harry Potter and the Half-Blood Prince is dull, exactly... No, the main problem is that J K Rowling has now written six of these bricks. Even if they were getting better, they're certainly not getting any fresher."