Is this a marketing gimmick/ploy, but whatever the case, this is a wise move. The book is a hit in the US, most especially for teens, and I believe that the movie adaptation will become a hit, too. But may not be as hit as the Harry Potter series.
“Twilight – the movie adaptation of Stephenie Meyer’s teen vampire novels – is be released early, in the slot left by the delayed Harry Potter film. The Twilight film from Summit Entertainment stars Kristen Stewart, recently seen in Into the Wild, and Robert Pattinson, who played Cedric Diggory in two Harry Potter films. The reason for this frenzy was the release of Breaking Dawn, the fourth and final part in Meyer’s vampire series, The Twilight Saga. The excitement is reminiscent of that created when a new Harry Potter used to hit the shops. Meyer’s Twilight books follow the story of Bella Swan, an ordinary high-school student who falls in love with the “vegetarian vampire” Edward Cullen.”
The complete story, from BBC News.