Humor is, of course, subjective, so I'll say this upfront: if the trailer for The Invention of Lying didn't appeal, you're probably not going to like the movie either. But for all the many, many high-concept comedies coming out of Hollywood these days, this concept is actually kind of brilliant: in a world where everyone only speaks the truth (and, by extension, tends to share every unpolite but honest thought in their head), one guy (Ricky Gervais) has figured out how to lie.
You'd think that concept might get old, creating a one-joke act that plays itself out far before the end. But with so much material within that concept, it doesn't. Maybe it's just me, but watching Tina Fey say how much she loathes her job and waiters telling Gervais that his date (Jennifer Garner) is way out of his league kept making me laugh. Best of all are some hilarious truth-in-advertising campaigns from Coke ("it's very popular") and Pepsi ("for when they don't have Coke.") Also, Jennifer Garner proves here that, just as in 13 Going on 30, she's actually quite a talented comedic actress, and her truth-telling is often the funniest. All of which makes the first act of the movie provides a frequent and consistent amount of laughs.
Writer/directors Gervais and Matthew Robinson knew they couldn't let the whole movie go on like that though, so, for better and for worse, it heads off in different directions. Trying to comfort his mother as she's dying, Gervais ends up inadvertently inventing religion. At first it seems like that shouldn't work (or belong in this movie), but once you see him try to explain "the man in the sky" to his followers in the movie's funniest scene, you'll change your mind.
Sadly, the last act reverts to what so many similar comedies feel obligated to do: go the tried-and-true romance route, with a Gervais/Garner will-they-or-won't-they you've seen about 500 times before, and each of them better done. Cause this time the central concept all but disappears (as does the humor) as Gervais mopes about wanting Garner back. As Gervais' character is basically an even more depressed version of Extras' Andy Millman, the movie illustrates that a movie about depressed characters is sometimes kind of depressing. And even if the truth-telling never gets old, the hundreds of times they say "genetic match" and "fat kids with snub noses" most certainly does.
You'd think the guy who created Tim and Dawn (who would eventually become Jim and Pam) could make a better romance, and find a balance between funny and sad instead of bouncing back and forth between them. Maybe that's what was lost in Gervais finding a new collaborator instead of usual co-writer/director Stephen Merchant (who does have a fun cameo). Speaking of cameos, the movie is packed full of them. I won't spoil them all, but they run the gamut from the more expected comedians (like Merchant) to legit big names (Edward Norton!) Guess there's a lot of fans of The Office (or Extras?) in Hollywood these days.
Basically, it's uneven. When it's good, it's hilarious. When it tries to be serious, it fails. But since it's the funny parts you'll remember when you leave the theater, I'm not lying when I say you should check it out.