Hollywood has always shown a fondness for adapting books - whether they be classic, contemporary or comic - into movies. Not only does this provide instant fodder for a script, but it guarantees a built-in audience.
It also comes with some inherent problems, including cutting the story to fit a movie timetable and translating the characters from the images readers create in their minds to the ones that appear on the large screen.
Director Andrew Niccol faced both problems with his film adaptation of Stephenie Meyer's "The Host." He handles only one of them successfully.
Niccol - working with Meyer - managed to edit the book of 600-plus pages into a workable and interesting script about an alien invasion. The bodies of humans have been taken over by space travelers who look like neon caterpillars. Only a few humans have escaped. The aliens suggest this invasion is good because it eliminated war and saved the environment. To humans, it means the loss of free will.
When an alien known as The Wanderer ends up in the body of the spunky Melanie Stryder (Saoirse Ronan), another problem arises. Melanie's not ready to give up her identity, and she and the alien begin living a dual relationship that gets even more complicated when the young woman makes her way back to her family, friends and boyfriend.
Niccol's script blends the kind of lofty topics that are the heart of sci-fi productions with a complicated love story that's made Meyer's books so popular. The romance elements are even more complicated than her "Twilight" tale: Two guys (Max Irons, Jake Abel) are in love with one girl with two personalities.
Diane Kruger adds the key element of tension, playing The Seeker, an alien committed to tracking down humans.
It's the portrayal of the Melanie / Wanderer character that causes the biggest problems in the movie. Ronan's performance is out of this world and she's one of the few young actresses who would even come close to making this character work. But despite her best efforts, the scenes where Melanie and The Wanderer argue in her head often come across as silly. It's the type of thing that works far better when it's read in a book than when it's seen onscreen.
The mental pingpong match takes away from the nicely paced story, beautifully shot scenes and interesting acting performances - especially by William Hurt. It's hard to get past the unintentionally funny way the close encounters of the body-sharing kind are portrayed.
• Rated: PG-13 for violence, sensuality.
• Director: Andrew Niccol.
• Cast: Saoirse Ronan, Diane Kruger, William Hurt, Max Irons, Jake Abel.
• Running time: 125 minutes.