Eleven-year-old Cassie Todd is looking forward to the new movie version of "Charlie and the Chocolate Factory," based on the beloved children's book by Roald Dahl. But Cassie has priorities.

When "Charlie" opens this weekend, she will be poring over "Harry Potter and the Half-Blood Prince," the sixth installment in J.K. Rowling's blockbuster book series.

Cassie, who turns 12 next week, is hosting a Harry Potter-theme birthday sleepover at her Takoma Park, Md., home. "We'll watch a Harry Potter movie, have dinner, then read chapter-by-chapter aloud," she says. Seeing "Charlie and the Chocolate Factory" will have to wait.

No doubt about it: "Charlie" is up against a champ. After a two-year wait, parents and children around the country are counting the minutes until "Harry Potter and the Half-Blood Prince" is released at 12:01 a.m. Saturday. Publisher Scholastic Corp. already has printed a record 10.8 million copies. One large online retailer has reported presales topping one million copies, while another says it has received more than 1.4 million preorders world-wide.

So despite anticipation for "Charlie," a $150 million product of Time Warner Inc.'s Warner Bros. Entertainment, the movie this weekend will be competing for the same family audience that is slavishly devoted to Harry Potter. If book buyers behave as they have during past outbursts of Pottermania -- staying up late to buy the latest installment at midnight, then rushing home to spend the weekend feverishly reading -- it could damp Charlie's debut.

In the movie business, that is crucial, as the all-important opening weekend typically sets the pace for a film's overall performance and establishes the word-of-mouth that helps generate hits.

"Charlie" already faces some challenges on that front: While some early reviews have been positive, director Tim Burton's quirky, sometimes dark take on the material may not agree with some parents (there is a brief, knife-wielding homage to "Psycho" at one point). And as the character Willy Wonka, Johnny Depp gives a performance that evokes comparisons to Michael Jackson -- not exactly what mom and dad may want to hear.

For a movie industry already in a period of decline -- by one yardstick, it appears to be heading toward its third straight down year in terms of admissions -- the Charlie-Harry smackdown is an ironic twist. Studio executives blame the lost market share on videogames and other high-technology forms of home entertainment, including their own DVDs -- a squeeze that has made it tough for Hollywood to turn expensive theatrical releases into the highly profitable enterprises of past summers, like Warner's "The Matrix Reloaded" and Sony Corp.'s "Spider-Man 2." Now, Warner Bros. is contending with intense competition from one of the world's most antiquated consumer products: a book.

As the maker of the Harry Potter movies -- the next of which, "Harry Potter and the Goblet of Fire," will be released in November -- Warner Bros. might have carried some sway in planning the book's release date. But studio executives, who committed to the July 15 opening for "Charlie" months before the book publishers -- Scholastic and Bloomsbury PLC -- chose July 16 for Harry, say they never seriously considered a switch.

"We were very aware ... that the dates were going to coincide," says Diane Nelson, Warner's executive vice president for global brand management. "But we are not concerned that there isn't plenty of room in the marketplace for both of these great forms of entertainment."

She may have a point -- especially if "Charlie" sustains a long run in theaters. Some die-hard Harry fans say they plan to see "Charlie" at some point, even if they don't make it during opening weekend.

"We are planning on seeing the movie Monday -- by then we will have read the book," writes Doris Herrmann, a Houston-area teacher and mother of three, in an email. "I would have planned the movie on Saturday, but the book release is much more important to us."

Nonetheless, "Charlie" could benefit from having a larger demographic reach than a Harry Potter book, which may be too sophisticated for the very young. Mr. Depp is a star, and he received raves in Walt Disney Co.'s family-friendly movie, "Pirates of the Caribbean: The Curse of the Black Pearl." Also, nostalgia for the Dahl book, first published in 1964, and for "Willy Wonka & the Chocolate Factory," the 1971 movie version, could buoy the "Charlie" theatrical run.

"Harry Potter has a very distinctive audience, but 'Charlie and the Chocolate Factory' is casting such a wider net as far as who that movie is really appealing to," says Tina Wells, chief executive of Buzz Marketing Group, which polls consumers aged seven to 24 for their reactions to various cultural events and products. In recent weeks, she adds, "I was surprised to see how many teens and young adults are interested in seeing the movie."

This weekend, book retailers are hosting 5,000 Harry Potter-theme parties around the U.S. In New York City, Jim Dale, the narrator of the Harry Potter audiobooks, will appear at a Barnes & Noble superstore's party that will include a taped broadcast of Ms. Rowling from Scotland.

Heidi Tandy, a Los Angeles attorney whose toddler wakes her up in the wee hours of the morning, envisions round-the-clock reading after buying the book early Saturday. Still, "I do wish (the studio) had scheduled showings of Willy Wonka at 9, then kept people in theaters till midnight and then handed the books down the rows," she writes in an email. "Would've made a great combination of magics!"