But the threat of spoilers hasn't ruined the party. Advance orders for the latest book have broken records and release celebrations are on tap across the country. "We expect the largest crowd in history to be at our stores Friday night at the stroke of midnight," said Barnes & Noble Chief Executive Stephen Riggio in an interview.

Scholastic expects to break both printing and sales records with the seventh book. The company said it has printed 12 million copies in the U.S., surpassing records held by the sixth book, which had a first-print run of 10.8 million in 2005. More than 6.9 million copies of the book were sold in the first 24 hours. "A very large first printing for a children's book would be 50,000," said Maureen O'Connell, chief financial officer for Scholastic. "This is unprecedented."

In years that the books are published, Harry Potter accounts for between 8% and 10% of Scholastic's $2 billion in revenues, O'Connell said. In years without a new book, sales account for less than 1% of revenues, she added.

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Meanwhile, Harry Potter book purchases are "outpacing the sale of adult books, even in this age of the Internet, MySpace, Facebook and video games," Barnes & Noble CEO Riggio said. "It has inspired kids to read the whole series, and it has made them more interested in reading." Barnes & Noble has taken 1.3 million advance orders for the seventh book, and the chain expects Saturday to be the company's biggest non-holiday sales day ever, Riggio said.