The publisher of the Harry Potter books called in the lawyers after a British supermarket chain accused it of "blatant profiteering" for charging £17.99 (€26.50) for the final novel in the series.
The dispute between Bloomsbury and Asda, the British unit of Wal-Mart Stores, erupted today just four days before the release of Harry Potter and the Deathly Hallows, widely expected to become the fastest-selling book of all time.
Bloomsbury said it cancelled a delivery of 500,000 copies to Asda stores across the country because of unpaid bills, but Asda believes the real reason is a statement it issued on Sunday in which it criticised Bloomsbury's pricing policy.
"Today, Asda pointed the finger directly at Bloomsbury for attempting to hold children to ransom by raising the recommended retail price on the final Harry Potter instalment," it said, adding that the pricing was "blatant profiteering".
The retail price of £17.99 for Deathly Hallowscompares with £11.99 for Harry Potter and the Philosopher's Stone, the first book in the series published 10 years ago.
That book was 223 pages long, compared with 608 pages for the seventh and last instalment.
Bloomsbury said the row started over "invoicing arrears" but escalated after the release of the Asda statement.