Talk about your magic books. One lucky American library is going to be able to cast a spell on its readers by displaying the first American edition of " Harry Potter and the Half-Blood Prince (search)," signed by J.K. Rowling (search) herself. It's the top prize in a sweepstakes from Scholastic, Inc., the American publisher of the series about the boy wizard.

Scholastic (search) was to officially announce the sweepstakes Wednesday morning.

The contest is open to every public library in all 50 states, with mailed entries due by June 30. The winning library will be selected and notified on July 1, but will have to keep the news quiet for the next two weeks. On July 15, representatives from the library will be presented with the signed book in New York. They will have to wait until 12:01 a.m. on July 16, the official release date of the book, to take permanent possession of it.

Barbara Marcus, executive vice president at Scholastic, said giving the first signed copy of the sixth book in the series to a library seemed a natural fit, since the Harry Potter series has been a blockbuster in encouraging children to read.

"It just made sense to match up Harry Potter ... and to connect it to a place where children get the exposure to a lot of books," she said.

For the release of the fifth book, Scholastic gave a signed copy to the New York Public Library.

But should library officials think that winning the book would be a windfall, with visions of eBay dancing in their heads, the rules are clear — it can't be sold. It must remain in the library's collection, preferably on display, and probably shouldn't even be loaned out.

Scholastic is publishing 10.8 million copies of the latest Harry Potter book, a record for U.S. publishing. The book has already been a top seller for months due to pre-orders..