The age of Potter VI officially dawned Saturday as millions of fans, from sweaty New York to chilly Australia, got their hands on "Harry Potter and the Half-Blood Prince" and began the darkest of J.K. Rowling's fantasy novels.

"I can't believe that I have the first copy," said 20-year-old Rachel Grandy, a student at Hunter College (search), who was first in line at the Barnes & Noble in Union Square, arriving early on a sticky summer morning and getting her book at midnight, some 16 hours later.

"It's totally boggling my mind right now."

In Edinburgh, Scotland, Rowling emerged at the stroke of 12 from behind a secret panel inside the city's medieval castle to read an excerpt from the sixth chapter to a super-select group of 70 children from around the world.

"You get a lot of answers in this book," Rowling, a resident of Edinburgh, said as she arrived at the castle, later settling into a leather easy chair before her adoring fans. "I can't wait for everyone to read it."

"Harry Potter and the Half-Blood Prince" is Rowling's most mature story, marked by the death of a major character and the arrival of love in the land of Hogwarts. Harry's fans can now solve the mysteries that Rowling teasingly hinted at for months: Will Harry's teenage friends Ron and Hermione find romance? Which character died? Who is the half-blood prince?

It has become publishing's most lucrative, frantic and joyous ritual: From suburban shopping malls to rural summer camps, fans dressed up, lined up and prepared to stay up late with their treasured copies.

In London, events were muted by the July 7 subway and bus bombings, which killed some 50 people. Book and magazine chain WH Smith scrapped a planned midnight launch at King's Cross Station, from whose fictional Platform 9 3/4 Harry catches the train to Hogwarts at the start of each term. The deadliest of the day's four attacks was on a subway near King's Cross.

"We're very much of the message that it's business as usual — London's open for business and we want to celebrate this book," said John Webb, children's buyer at Waterstone's, which said 300,000 people attended midnight openings at more than 100 stores across Britain.

In Australia, 17-year-old Mohammed Jalili-Baleh was first in a line of hundreds of would-be witches and warlocks at one of Sydney's largest bookstores. He and a friend spent more than 12 hours waiting on the cold sidewalk.

"I'm an obsessed fan," he said of the books. "They grip you. When you read one sentence, you don't want to put it down."

At the Wangfujing Bookstore (search) in downtown Beijing, about 40 people lined up in the early morning to buy "Half-Blood Prince." Rowling's books are so popular in China that an unknown Chinese author once produced an entire fake adventure, "Harry Potter and Leopard-Walk-Up-To-Dragon."

It was a kooky midnight countdown at the Barnes & Noble in Union Square, as a person in a white owl suit emerged from behind green curtains with a box and slowly walked over to a cash register. The owl handed the box to workers behind the counter and the first book was removed. Jim Dale, the beloved, multivoiced narrator of the audio books, began reading.

Since Rowling first introduced Harry and his fellow students at Hogwarts School of Witchcraft and Wizardry to the world in 1997, the books have become a global phenomenon, selling 270 million copies in 62 languages and inspiring a series of movies. Rowling is now the richest woman in Britain, with a fortune estimated by Forbes magazine at $1 billion.

With only brief interruptions, "Half-Blood Prince" has topped the charts of Amazon.com and Barnes & Noble.com since last December, when Rowling announced that she had completed it. Pre-orders worldwide already are in the millions and other Potter products are selling strongly, including the audio book, a "deluxe" edition of "Half-Blood Prince" and a box set of the previous five books.

Publication has sparked a price war in England, with many chains selling the book for about half the $29.95 cover price. In the United States, the online retailer Alibris.com is offering $5, plus postage, for used copies. Scholastic Inc., Rowling's U.S. publisher, has also joined the competition, offering a 20 percent discount on its Web site.

"I am always disappointed when publishers sell books directly to the consumer, bypassing their retail partners," said Mitchell Kaplan, president of the American Booksellers Association. "Selling it at a discount makes it more frustrating."

Scholastic is releasing more than 10 million copies. Waterstone's predicts 2 million copies will be sold in Britain, where Bloomsbury publishes the book, and 10 million worldwide in the first 24 hours.

The new work has been preceded by months of publicity, hype and plot leaks, and surrounded by intense security. Amazon.co.uk has a secure 200,000-square-foot warehouse to pack the books. Canadian publisher Raincoast sought a court injunction after a Vancouver store accidentally sold 14 copies last week. A judge ordered customers not to discuss the book, copy it, sell it or read it before its release.

Even the pope has been joined to Pottermania. Writer Gabriele Kuby (author of "Harry Potter — Good or Evil?") said that Pope Benedict XVI told her in letters written in 2003, when he was Cardinal Joseph Ratzinger (search), that the books "deeply distort Christianity in the soul."

The Vatican had no comment.