JK Rowling has hit out at US newspapers that have published plot details from the final Harry Potter book.
JK Rowling said fans wanted to finish the saga "in their own time"
The author said she was "staggered" that papers including The New York Times had printed reviews ahead of the novel's publication on 21 July.
The author said the information was in "complete disregard of the wishes of literally millions of readers".
UK publishers Bloomsbury said spoilers remained "unauthenticated". Some books have been sent out early in the US.
The book's US publisher Scholastic has sued online retailer DeepDiscount.com for breaking the strict embargo by dispatching a number of copies.
The novel has also appeared on auction site eBay, while pictures of what appeared to be pages from the new book have appeared on the internet.
The book's contents have been the subject of intense speculation
Bloomsbury said it was "dismayed" to learn about the early sales. But internet spoilers had not come from the few copies sold ahead of the official publication, it insisted.
The strict embargo was being "enforced unflinchingly and without exception" by publishers in 93 countries, the company added.
Rowling said the US newspaper reviews would particularly affect children "who wanted to reach Harry's final destination by themselves, in their own time".
"I am incredibly grateful to all those newspapers, booksellers and others who have chosen not to attempt to spoil Harry's last adventure for fans," she added.
Rowling's statement follows an earlier message on her website, in which she said: "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 New York Times said its copy was bought at a store in the city on Wednesday.
The paper's books and theatre editor Rick Lyman said: "It's our policy that once a book has been offered up for sale, it's fair game to be reviewed.
Some fans are already queuing outside a central London bookshop
"It's not our business to help book publishers market their books. We tried very, very hard to give away the absolute bare minimum of the plot."
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.
A person selling a copy on eBay said: "I don't work for a bookstore and I don't have a magic wand. An online store shipped a copy early."
Meanwhile, UK supermarket Asda has announced it will sell the book for £5 - just over a quarter of the recommended retail price.
Bloomsbury had originally cancelled Asda's order, with the supermarket calling the price "potty" and accusing the retailer of "blatant profiteering".