Comicbooks are starting to do double duty in Hollywood.

It seems as if every day, a new deal is announced to turn a graphic novel into a high-profile feature like “300,” “Watchmen” or “Wanted.”

Development executives love the books, since they give a visual sense of what a film and its characters may end up looking like on the bigscreen.

But filmmakers are now hoping the launch of new comics will help promote properties moviegoers may not necessarily be familiar with before films bow at the megaplex.

Paradox Entertainment, the company that’s developing a reboot of the “Conan the Barbarian” film franchise, inked a deal last week with Dark Horse Comics that will launch books for characters, created by pulp writer Robert E. Howard, that the shingle wants to turn into film franchises.

While Conan may be familiar among the masses, Dark Agnes, El Borak, Cormac Mac Art and James Allison are more obscure characters.

Earlier this year, Paradox and Dark Horse began publishing a series of Solomon Kane books to promote the shingle’s upcoming actioner, based on the character played by James Purefoy.

“Although it’s a legacy character, a new generation had never heard of him,” says Paradox president and CEO Fredrik Malmberg, who hopes the books help introduce the 16th-century swordsman to audiences, while turning into a viable publishing biz for the shingle.

Comicbooks like “Solomon Kane” often serve as prequels and establish characters, flesh out backstories and the overall world or storyline that will drive the pic’s plot. The goal is to interest a new generation of fans who will recommend the film to others through a flurry of Internet chatter.

This summer, comicbook prequels were published to hype Paramount’s reboot of “Star Trek” and Warner and Sony’s “Terminator Salvation.” A new series of books was handed out at last week’s Comic-Con to tubthump Par’s “G.I. Joe: The Rise of Cobra.”

In fact, the interest in comicbooks has grown so much in Hollywood that publishing one to help drive a pic has become a standard piece of a film’s marketing campaign — especially for major tentpoles.

“Studios have come to the realization that having a presence out there and the ability to build interest is valuable to a film,” says Dark Horse prexy Mike Richardson. “We reach the same demographic the studios are trying to reach,” namely 16- 30-year-old males.

Because of that demo, Malmberg sees comicbooks as “one component of a character or franchise launch.”

But it’s a strategy that needs to follow a set of rules in order to strike a chord.

“You have to do the book for the love of the game and not as a crass marketing play,” says one studio marketing maven.

While that’s easier said than done, it’s why Paradox turned to Dark Horse — the company is producing films (its recent credits include the “Hellboy” films and “30 Days of Night”), but publishing comicbooks is Dark Horse’s core business.

“We tap into their editorial knowledge, so we’re not just Hollywood types wishing for comicbook sales,” Malmberg says. “You can’t fool the readers. If it’s not a comicbook, they don’t want to read; they’re not going to buy it. And if they don’t buy it, they don’t help your movie.”

Dark Horse prefers publishing prequels that end right where the movie begins.

“We’re happy to do the straight adaptations, but those are less fulfilling,” Richardson says. “You’re just retelling the story you’ll see in the theater.”

It’s too early to tell whether comicbooks can serve as an effective marketing tool.

In the overall comicbook market, DC and Marvel overwhelmingly dominate the charts each month with their lineup of superheroes, creating little room for movie-based books to break through. And like other media, the comics biz is struggling, with a 10% decline in sales this year.

Yet TV networks have launched successful books to promote “Fringe” and “CSI,” and keep older ones like “Angel” alive with fans. “Buffy the Vampire Slayer” moves around 100,000 copies per run for Dark Horse. Even videogame companies have launched books for “World of Warcraft,” “Mirror’s Edge” and, soon, “Mass Effect” among others, to promote titles.

For a book to be considered successful, it needs to move 20,000 units per issue. Generally, trade paperback collections wind up breaking even or generating profits sincethey have a longer shelf life, carry higher pricetags and are sold at large bookstores.Books for “Star Trek,” “Star Wars” or “Transformers” have been successful “because the fanbase is so rabid,” says one senior comicbook agent. “The material sells no matter what.”

A prequel setting up the first “Transformers” pic in 2007 was expected to sell a strong 50,000 copies overall, but wound up moving more than 1 million books for IDW Publishing. Another prequel book for this summer’s sequel has also sold well.

Sales like that are usually unreachable for more unknown titles. Most wind up losing money.

Summit Entertainment sold only around 20,000 copies for a six-issue series, published by DC Comics’ Wildstorm division, to promote its sci-fi actioner “Push.” The run ended in February.

Paradox has done better with “Solomon Kane,” so far. Its first five books have sold more than 57,000 copies.

“Comicbooks do a better job at helping set up a movie or TV show at a studio,” says an agent who reps comicbook publishers and clients looking to adapt them or launch their own. “That’s where you’re going to make the most money. More obscure properties aren’t going to sell enough to warrant attention.”

Yet even if the books aren’t successful, studios aren’t risking too much by publishing them, at far less than $1 million for a run.”We view comicbook publishing as a viable business that stands on its own,” Malmberg says. “It’s a profitable and growing business for us. You have to see the comicbook as one piece of a much broader launch so that the film becomes the big tentpole and all the other things can support it. This is a town of hype, so any buzz for a project is positive.”