By Stephen M. Silverman
June 20, 2003 11:19 AM

As the clock ticks away until Saturday’s arrival of “Harry Potter and the Order of the Phoenix,” its author, J.K. Rowling, is already typing away on the next one — already tagged “Harry 6” — her British publisher, Bloomsbury, announced Friday.

No deadline has been set for the next book, reports Reuters.

Bloomsbury Chairman Nigel Newton says in a statement that he was “delighted” with the response to “Order of the Phoenix,” the fifth book in the successful series — which is expected to become the fastest-selling and most profitable book of all time.

In its review of “Order of the Phoenix,” published Friday, the Associated Press, applauds the book’s scope and says the much-delayed, 870-page tome is a “deeply satisfying … rich feast” that “was worth the wait. And then some.”

By Saturday night, Rowling, 37, will reportedly be $50 million richer than she was on Friday. All told, 8.5 million copies of “Order of the Phoenix” will be ready to meet this weekend’s demand, and the Scottish-born Rowling, whose fortune is already estimated to be greater than Queen Elizabeth’s, will probably make another $85 million from “Phoenix” — bringing her total earnings from her books and their spin-offs to $577 million, according to educated estimates.

The first four “Potter” books have sold almost 200 million copies in 55 languages and 200 countries.

Rowling plans to write a total of seven books about the adventures of Harry and his friends at the Hogwarts School of Witchcraft and Wizardary — and, as always, the future editions will be cloaked in secrecy.

Regarding the secrecy surrounding the plot of “Phoenix,” Rowling tells the BBC: “One could be cynical … and say it was a marketing ploy, but I don’t want the kids to know what’s coming, because that’s part of the excitement of the story.”

She added: “And having sweated blood over my red herrings and to lay all my clues … it’s a very important part of my life.”