Harry Potter author Joanne K Rowling said on Thursday she was "staggered" that pirate copies and reviews of her last volume had appeared in the media.
"I am staggered that some American newspapers have decided to publish purported spoilers in the form of reviews in complete disregard of the wishes of literally millions of readers, particularly children, who wanted to reach Harry's final destination by themselves, in their own time," Rowling said.
The author at the same time expressed her gratitude to those media who had not spoiled the suspense.
"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," Rowling said.
The New York Times among others published a review of the seventh and last volume of Harry Potter and the Deathly Hallows, however without revealing the exact end.
A US retailer had earlier delivered 1,200 copies, following which Internet file-sharing sites circulated scans from the ostensibly real book.
The British publisher Bloomsbury said he was "extremely dismayed" by the early deliveries.
The reviews might be based on fake copies, it added.
A Bloomsbury spokeswoman said the release date and time embargo of 0001 British Standard Time (2301 GMT) on Saturday, July 21 was "being enforced unflinchingly and without exception by the publishers".