In the world according to "The Invention of Lying," truth rules because no one has thought of the alternative. Bus advertisements for Coke keep it short and simple ("It's very famous"). First encounters are brutal affairs ("Hi. I'm threatened by you"), full of small talk and the sort of thing typically kept inside one's head.

The new comedy from writer-directors Ricky Gervais and Matthew Robinson stars Gervais, the droll force behind the BBC version of "The Office," as a sad-sack screenwriter in this alternative universe. Mark Bellison works for Lecture Films (the only kind of films available), and given that his specialty is the unglamorous 14th century, he has had a difficult time getting the respect of his cohorts lately.

And then comes the epochal First Lie Ever. "The Invention of Lying" contrives a romance between Mark and Anna, played by Jennifer Garner, who is attracted to Mark's smugly unctuous co-worker ( Rob Lowe) but comes to realize that beauty is more than skin deep.

The movie may be a little softer than you'd expect from Gervais, and it's certainly not much to look at. Yet the premise is so rich, and some of the variations on the central theme are so clever, you forgive the problems. Listening to Mark concoct the notion of religion, and explaining it to a group of people never before confronted with such a concept, you realize Gervais' brand of comic charisma -- chipper yet somehow dour -- is like no one else's.

Gervais played the lead in " Ghost Town," a comedy too few people saw. That film's central character started off hard-edged and then softened, plausibly; I wish "The Invention of Lying" weren't quite so determined to make Mark an object of audience sympathy before testing him. Part of this may be Gervais and Robinson looking for ways to make Gervais "relatable" to American moviegoers relatively unfamiliar with his skill set. The best bits in the film let Gervais be himself, learning to dissemble and loving it, before taking things too far.