The US publisher of Harry Potter and the Deathly Hallows is taking legal action against two companies for dispatching copies of the book early.
Publishers have placed a strict embargo on the book's publication
Scholastic sued online retailer DeepDiscount.com for breaking the strict embargo of 21 July.
In court papers filed in Illinois, the publisher also named its distributor Levy Entertainment for failing to ensure books were not sent out.
It said only a tiny fraction of its 12 million copies had been distributed.
"The number of copies shipped is around one one-hundredth of one per cent," said Scholastic in a statement.
The company added that they had a list of customers who had ordered the book from DeepDiscount.com and were asking them to put it to one side if they have already received it by mistake.
A report in The Baltimore Sun newspaper about a customer who had already received his copy prompted Scholastic to take action.
Scholastic is seeking unspecified damages from the two companies for "complete and flagrant violation of the agreements that they knew were part of the carefully constructed release of this eagerly awaited book".
A spokesman for Infinity Resources, who own DeepDiscount.com, said: "We take the situation very seriously and are conducting an internal investigation."
JK Rowling has called on fans to dismiss speculation
Levy Entertainment declined to comment.
Scholastic has also asked "everyone, especially in the media, to preserve the fun and excitement for fans everywhere".
Harry Potter author JK Rowling has also posted an appeal on her official website, stating: "Let's all, please, ignore the misinformation popping up on the web and in the press.
"I'd like to ask everyone who calls themselves a Harry Potter fan to help preserve the secrecy of the plot for all those who are looking forward to reading the book at the same time on publication day.
"In a very short time you will know everything!" the statement concluded.
'No magic wand'
On Wednesday the Baltimore Sun printed a review of the book, saying it had obtained a copy from a relative of one of its reporters who had received it prematurely.
It says Rowling's seventh book "lacks much of the charm and humour that distinguished the earlier novels" but makes up for it with "hard-won wisdom".
On the same day, another copy was being offered for sale on internet auction site eBay by a seller who claimed to have received a copy ahead of the release date.
Some fans are already queuing outside a central London bookshop
"I don't work for a bookstore and I don't have a magic wand," the seller wrote. "An online store shipped a copy early."
Earlier this week, pictures of what appeared to be pages from the new novel were circulating on the internet.
Minna Fry, marketing director of the book's UK publisher Bloomsbury said: "There have been so many fake books going up on the internet over the past four to six weeks. We have no reason to believe that these are anything other than fake either."
Scholastic issued a subpoena on Monday to California-based social networking site Gaia Online in connection to user-posted material on the book.
In a statement, the website said the link had been immediately removed and that the user in question had been banned for 14 days.
Scholastic also ordered photo-sharing service Photobucket to remove Potter-related material from its site.