Witches and wizards have only two days left to polish their wands and get their best robes out of the wardrobe.

For those eager to get their hands on one of the 10.8 million copies of “Harry Potter and the Half-Blood Prince,” the nation’s bookstores, Wal-Marts, and fan sites are planning more than 5,000 “midnight parties,” a spokeswoman for the book’s publisher, Scholastic, Jennifer Pasanen, said. Booksellers in New York began receiving their tightly guarded shipments of the sixth Harry Potter book yesterday.

At 12:01 a.m. Saturday, the book goes on sale, and readers can learn just who exactly the Half-Blood Prince is. That’s also when the publisher’s “100-Day Countdown to Harry” campaign, which was launched April 7 and has included advertisements in newspapers and on billboards, airplanes, and the Web, reaches its climax.

Chain and independent bookstores throughout New York City are planning celebrations, as are the New York Public Library and the Affinia 50 hotel in Midtown, which is offering a weekend package that includes treats such as chocolate frogs, Potter punch, and of course a copy of the new book.

“Ours will be one of the biggest parties in New York,” the owner of the Chelsea bookstore Books of Wonder, Peter Glassman, said of the store’s Friday-night bash, where 2,000 people are expected. The festivities start at 11 p.m. and feature an appearance by a minor “Potter” celebrity, the cover-illustrator of the American printings of all six “Harry Potter” books, Mary GrandPre. The store also plans to have live owls on hand. A raffle features such prizes as posters created by Ms. GrandPre and a first edition printing of a Harry Potter book signed by the author, J.K. Rowling. The bookstore expects to have all 25 of its employees on duty.

“We throw events for book releases, but never like this. We expect to sell a couple of thousand books in the first few weeks,” Mr. Glassman said.

While it is not subsidizing the “midnight parties,” Scholastic has been working with individual book retailers to plan such events by giving stores promotional materials such as CDs, posters, and lightning-bolt temporary tattoos.

“Each event will have its own feel,” the publisher’s vice president of franchise management, Ms. Pasanen, said.

The Barnes & Noble at Union Square is throwing a Midnight Magic Party, which features the actor Jim Dale, the voice of the “Harry Potter” audiotapes.

The Barnes & Noble on Seventh Avenue in Park Slope is planning a Witches and Wizards Costume Contest for “muggles” under age 12. The writer Ned Vizzini, one of the judges, said he’ll be looking for “ingenuity and ability of the costume to appeal to those who don’t know ‘Harry Potter’ intimately.” Mr. Vizzini himself has read only the first Harry Potter book.

“I’m most excited for the prizes,” Mr. Vizzini said, referring to the extravagant gifts the winners of the contest will receive.

The first-place winner receives a racing broom, the second-place winner gets a 14-inch mahogany wand in a velvet case, and the third-place winner walks away with a Sorting Hat, the hat used in the books to sort new Hogwarts students into the academy’s four houses.

Bookstores aren’t the only beneficiaries of the craze. On West 21st Street in Manhattan, the owner of Abracadabra Magic & Costumes, Paul Blum, said: “‘Harry Potter’ stuff has been selling like crazy.”

The hype surrounding the literary phenomenon is a boost for summer business, especially at Columbia University Bookstore, which typically experiences a slump when the normal school year ends.

“We’re dependent on the university for much of our foot traffic,” an employee, Beth Niemczyk, said. This week, the bookstore plans its first “Harry Potter” release party.

“We expect to see a lot of high school students because there’s currently a high school program on campus,” Ms. Niemczyk said. The bookstore will be screening all three “Harry Potter” movies beginning at 10 a.m. Friday leading up to the night’s party, which features face-painting and refreshments.

Borders stores, including locations at Park Avenue, Broadway, and Columbus Circle, are holding Midnight Magic parties with up to six craft stations. The parties will revolve largely around Scholastic products, according to the general manager of the Borders at Columbus Circle, Michael Kelly.

“The party is just a way to celebrate the books and give people something to do until 12:01,” he said.

The parties are open to the public and no reservations are necessary, though thousands of fans have placed orders for the book in advance.

Some stores are forgoing parties and simply staying open late, such as the Shakespeare & Company on Broadway, which usually closes at 11 p.m. on Fridays but this week will be open until 12:30 a.m. Saturday.

One Potter party that won’t burn the midnight oil is the New York Public Library’s. Its Friday fete, at the Donnell Library Center on West 53rd Street, will run between 3 p.m. and 5 p.m. and will include music, contests, and games.

“It’s become sort of part of our summer reading program,” a library spokeswoman, Jenny Verte, said of the Potter release. “We encourage kids to come in and read anyway, and this book really gets kids reading, so it’s great.”

Those who don’t want to see $30 magically disappear from their pockets will be able to take the new book out of the library. The New York Public Library placed its largest order for a single title, ordering 12,786 copies of “Harry Potter and the Half-Blood Prince.” Officials are encouraging readers to place orders online to assure themselves a copy of the book.

As Scholastic has its headquarters in New York, it is throwing its own celebration, closing down Mercer Street, between Prince and Spring – the block behind its corporate office – between 8 p.m. and 11 p.m. and transforming it into Harry Potter Place.

“We’re really going to try to create a sense of Hogwarts,” Ms. Pasanen said. The activities designed to “really tap into ‘Harry Potter'” include live owls and a “scientist and magician” who will “create magic potions.”

The official midnight parties started with the publication of the fourth Harry Potter book, “Harry Potter and the Goblet of Fire.” Their development into a widely observed event is a testament to the devotion of the series’ fans – and the commercial payoff of a much-anticipated midnight release date.

“We always set a publication date, and a few retailers wanted to know if they could open at 12:01 so people could get their books at the first, best moment,” Ms. Pasanen said. When fans flooded bookstores at the late hour to get their hands on a copy of “Goblet,” a tradition was born.

The timing of the release and the corresponding parties is not ideal for all devoted fans, however. “Harry Potter” lovers who are observant Jews cannot purchase the books on Friday nights because of the Sabbath. Additionally, some parents of younger fans feel that midnight is too late an hour for kids to be gallivanting about.

For true fans, it’s not just about midnight. Spellbound 2005, a mega-celebration at a shopping center in Mount Prospect, Ill., is expected to draw thousands of fans from all over the country with activities starting at 10 a.m. Friday. They include a land-based version of the wizarding sport Quidditch, a human chess game, and three rooms reserved for discussion of the books.

One of the entertainers at Spellbound is the Massachusetts-based rock duo Harry and the Potters. The band’s songs tie into events and characters in the Harry Potter books, but the musicians have not yet worked on any new material related to the sixth book. “We try not to speculate,” one of the band members, Paul DeGeorge, said.

After Spellbound, Harry and the Potters will be embarking on a national tour in their van. The closest stop to New York City is an engagement August 13 at Shirley, on Long Island.

“We’re planning on reading the book in the car, then writing some new songs,” Mr. DeGeorge said.

For party-witches and wizards out there who still don’t have plans for Friday night, Scholastic has set up a Web site listing “Harry Potter” parties taking place across the country.

Ms. Rowling, the author, won’t be on North American shores: She is scheduled to read the first few words of the first chapter of “Harry Potter and the Half-Blood Prince” at Edinburgh Castle.