But the adaptations hitting theaters this week didn't need a novel's characters or built-in narrative, just a well-known brand name.
The must-read pregnancy manual "What to Expect When You're Expecting" has become an all-star comedy romp about the pitfalls of new parenthood. The book is full of helpful advice, "but it's almost like a medical manual," said Shauna Cross, who co-wrote the screenplay. "That's not that entertaining to go and watch."
So the cinematic version, opening Friday, stars Jennifer Lopez, Cameron Diaz, Chris Rock, Elizabeth Banks, Dennis Quaid and others in intertwining tales about various experiences of pregnancy, from infertility and miscarriage to trouble-free twins.
Also opening Friday is "Battleship," an action flick inspired by the 45-year-old board game starring Taylor Kitsch, Liam Neeson, Brooklyn Decker and Rihanna. Based on finding a hidden enemy by searching coordinates on a grid, the classic game may be best known to some readers by an old TV commercial in which an exasperated player proclaims, "You sank my battleship!" The film, set during a war games exercise on the Pacific Ocean, shows how the U.S. Navy might respond to an alien attack at sea.
"There are certain elements from the board game that lent themselves well to the DNA of a movie," said director Pete Berg. "Two enemies trying to locate and kill each other violently is, good god, a movie... The rest is classic creative endeavor."
Coming up with characters and narratives around popular brands that intrinsically have neither one has become business as usual in Hollywood.
"With movies costing so much, studios are looking for any kind of a hook that would ring a bell with an audience," said veteran film critic Kenneth Turan, who writes for the Los Angeles Times. "It's the same reason why they have all the sequels and things from TV shows and remakes: They're desperate to ring that bell."
Still, seizing on a popular brand doesn't guarantee a successful film.
The 1985 film version of the board game "Clue" flopped (though it later gained a cult following). But "Transformers," based on Hasbro's shape-shifting robot toys, became a multi-billion-dollar global franchise.
Berg said turning "Battleship" into a movie "was one of the great and really fun creative challenges of my career." The film has collected $215 million so far overseas, where it has been open for nearly five weeks.
As with "Battleship," adapting advice books such as "What to Expect When You're Expecting" and Steve Harvey's 2009 dating guide, "Act Like a Lady, Think Like a Man," requires writers to develop characters and story lines that aren't in the books.
"Think Like a Man," which topped the box office for two weeks when it was released last month, successfully spun Harvey's book into a romantic comedy following five couples navigating their relationship issues.
"One of the main challenges of an adaptation like this is the book already has a loyal following," said producer Will Packer. "All you can really do is mess it up. It's very tough to elevate it and take it beyond."
The appeal of tapping such a successful book as source material is, of course, that it "potentially has a built-in audience," Packer said. "It helps you cut through the clutter in a very, very crowded marketplace in terms of the outlets and mediums trying to get attention from consumers."
Still, those who relied on "What to Expect" during their pregnancies won't really find the book's advice on screen.
"It's the source material we wanted to include, but there's so little there that was actually used," said Heather Hach, who co-wrote the screenplay. "It's not an adaptation in the truest sense, but without this wonderful pregnancy bible that countless women have consulted, the germ wouldn't have been there."
Director Kirk Jones said that while some have called adapting the pregnancy handbook "desperate," anticipating a baby is a naturally funny experience.
"Just stop and look beyond the manual and think about pregnancy and that nine-month period: It affects guys and it affects girls in the most extraordinary ways," he said. "It was really just taking the essence of the book... You're basically enhancing the brand, because people are already familiar with the title."
The book's author, Heidi Murkoff, is one of the film's executive producers. Hasbro's president and chief executive, Brian Goldner, is a producer of "Battleship."
Hach said guidebooks are great for adapting into movies: "What's interesting about advice books is there are so many ways to tackle a problem. There are so many ways to think about a situation, and that's what our characters are doing."
Turan, the film critic, expects the trend to continue, whether or not the results are worthy.
"This is not about making good movies. It's about getting people into theaters... Everything else is secondary," he said. "They might make a movie out of Scrabble."
AP Entertainment Writer Sandy Cohen is on Twitter: www.twitter.com/APSandy.