The first four "Twilight" movies earned $2.5 billion at theaters worldwide, propelled by passionate fans of a book series about a vampire-and-werewolf teen love triangle. Box office watchers project "Breaking Dawn - Part 2" will haul in $150 million at U.S. and Canadian theaters this weekend, one of the year's biggest film debuts.

Eager to replicate that performance, studios executives have been trolling through young adult novels with the dream of uncovering the next big blockbuster franchise, paying as much as $1 million to secure the film rights to the hottest books.

At least four films based on books for teenagers will reach theaters next year, with young love forced to overcome alien parasites, evil zombies and other supernatural bad guys.

Executives hope they can uncover a story that excites tech-savvy teens, who supercharged the buzz mill for "The Hunger Games" and other hits by spreading the word to friends through social media posts.

"It's a very enthusiastic and deep passion that young people feel for a book they love," said Nina Jacobson, producer of "The Hunger Games," which spawned a blockbuster film franchise with $687 million in worldwide ticket sales this spring.

"When they love something, they share it," Jacobson said.

The four-year "Twilight" movie saga lifted tiny studio Summit Entertainment into Hollywood's big leagues and paved the way for its $412 million acquisition in January by Lions Gate Entertainment, the studio behind "The Hunger Games."

The coming young adult films incorporate paranormal themes like those in the "Twilight" movies or dark dystopian futures and battles for survival reminiscent of "The Hunger Games," and do it through the drama of young love.

Summit is aiming to get "Twilight" fans buzzing about next February's zombie romance "Warm Bodies" with a trailer before "Breaking Dawn - Part 2." "Warm Bodies" star Teresa Palmer chatted about the movie - a love story between a zombie and human - while she strolled the red carpet at a "Breaking Dawn" premiere.

A couple of weeks after "Warm Bodies," Warner Brothers will trot out fantasy movie "Beautiful Creatures," about a teen girl with magical powers and a boy who is drawn to her, with a debut on Valentine's Day.

The movie "shares as much in common with 'Twilight' as it does with 'Harry Potter,'" said Andrew Kosove, co-president of production studio Alcon Entertainment, referring to the boy-wizard series that grossed $7.7 billion in worldwide ticket sales and woke up Hollywood to the power of adaptations of children's and young adult books.

In March, Open Road Films releases "The Host," a science fiction tale about alien parasites from "Twilight" author Stephenie Meyer. Sony Corp's "The Mortal Instruments: City of Bones," about a teen girl who tries to protect the world from demons, comes out in August. Summit's drama "Ender's Game," the story of a boy who leads the charge against an alien invasion, is scheduled for November 2013.

They will battle the latest installments of existing young adult franchises such as the "Hunger Games" sequel "Catching Fire" that comes out November 2013. Warner Brothers will release "Hobbit" movies in December 2012 and December 2013.

The fever for young adult movies is so hot among Hollywood executives that studios snap up the rights to some books before they hit store shelves to keep them out of the hands of their competitors. Screen Gems, a unit of Sony, announced October 9 it had bought rights to "Black City" a month before the book went on sale.

The studio moved quickly based on a "high level of anticipation for the property in the online community and other young adult circles," it said in a statement.

Lions Gate's Summit studio scooped up the rights before publication for "Divergent," a novel set in a futuristic Chicago where people are divided into factions based on personality traits. The studio is producing a movie for 2014 that features young Hollywood star Shailene Woodley, who played George Clooney's troubled daughter in the movie "The Descendants" last year.

The "Divergent" book series has sold more than 2 million copies, pacing ahead of both "Twilight" and "The Hunger Games" at the same point in their histories, Lions Gate CEO Jon Feltheimer told industry analysts on a November 9 conference call.

"We are putting out to our fans right now we think that this is the next big franchise," Feltheimer said.

The web is producing hot properties, too. Media Rights Capital plans to develop three movies based on writer Amanda Hocking's "Trylle Trilogy" about a young girl with special powers.

Hocking gained fame by selling more than 1 million copies of self-published books on the Internet, an unusual feat that demonstrated fans' rabid support for the stories, said Media Rights Capital Co-CEO Modi Wiczyk.

"There is clearly a pre-existing audience," Wiczyk said. "It makes life easier."

Still, there is no guarantee book lovers will flock to a movie version of their favorite read, said Keith Simanton, managing editor of movie website IMDB.com. Film adaptations of "The Seeker" and "The Spiderwick Chronicles" failed to give birth to the kind of big movie franchises that have become the lifeblood of Hollywood's movie studios, he said.

"It is going to continue to be a trend, until one of them fails in a big way," Simanton said.

(Reporting By Lisa Richwine; Editing by Claudia Parsons and Chris Gallagher)

(This story corrects Jacobson's job title in the sixth paragraph to producer from executive producer)

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