London, July 17 (Reuters): Bookstores around the world tallied sales of the sixth Harry Potter installment today, but after the eagerly awaited global launch, the magic was wearing off for some.

Harry Potter and the Half-Blood Prince is expected to be the fastest-selling book in history, with British retailer Waterstone’s forecasting that 10 million copies would have been snapped up worldwide during the first 24 hours of trade.

Underlining the anticipation surrounding the book, instant reviews appeared on the Net within hours of the release, most of them favourable. Young readers picked up on the darkness of the plot. “With its dramatic, violent conclusion, this book is by far the darkest and unsettling HP yet,” wrote 12-year-old Indigo Ellis in The Sunday Telegraph. “Maybe it will leave a few more seven-year-olds in tears. But it also makes it the best so far.”

A sizeable minority of older readers, however, was less than impressed by the 607-page work. “It’s wordy, flabby and not very well edited ? perhaps a bit less inventive than previous ones,” wrote Suzi Feay, literary editor of Britain’s The Independent on Sunday.

Author J.K. Rowling, 39, said she had already finished the final chapter of the last book in the series. Fourteen-year-old Owen Jones, who won a competition to hold a rare interview with the writer, asked Rowling if she was looking forward to completing the Harry Potter series.

“I’m dreading it in some ways, because I do love writing the books and it’s going to be a profound shock to me, even though I’ve known it’s coming for the past 15 years,” she said.

Some sought to put the Harry Potter phenomenon into perspective. “Oh for a timely spell of reality,” Roland White wrote in the Sunday Times.

“Let’s keep things in perspective. Until Friday, the Harry Potter series had sold about 270 million copies worldwide. Which is considerably less than the one billion shifted by the late, rather unfashionable, Barbara Cartland.”