You should know where you are with Ricky Gervais. He's given us enough clues. Is he the multi-award winning comedy writer/director and performer who has cornered the market on the comedy of embarrassment and placed himself in the role of the quintessential overweight loser squarely (or roundly) in the mind of his public? Or is he a smug, self-satisfied and deluded everyman with the luck of the gods? The answer is, of course, all and none of the above. He'll probably admit to being lucky but then the harder you work the luckier you get. His stand up persona and podcast character are very telling indications of what sort of a man is Ricky Gervais (not that we should care but it is a tad pertinent to a review of his latest which is, to say the least, 'Gervaisian'). There is an abyss of difference between the podcast Ricky and the stand-up Ricky. The word 'polarised' comes to mind. Let's not even take a stab at who is the real Ricky.

The vain, cocky, 'world in his hands', king of comedy performer on stage gives way to a bright, thoughtful and often hysterically amused ordinary bloke in his podcasts particularly those featuring the extraordinary outpourings from the tangential-to-reality mind of a certain Karl Pilkington. I suspect Gervais is 90% of the latter alter ego. Yes, he has whored for Microsoft (that makes me flinch a lot) and there are some disquieting indications of (playful?) physical abuse from on high in the extras of Extras (behaviour even partner Stephen Merchant seems reluctant to condone) but there is also something innately honest about the guy that I can't define or dismiss. It also helps that he's an out and out atheist which gives some definition and weight, flimsy or not, to his latest movie and US directorial debut, The Invention Of Lying.

OK, I'm biased. There are some not a million miles away from this site who would not cross a road to spit on the man if he were alight. It's easy to take the media hyped bullshit and that stage persona as the real thing but I suspect it's the Gervais act – the trademarked insensitive and risqué comedian who happens to dominate a lot of media outlets since The Office went stratospheric. Then again how can you know anyone except their often heavily managed persona if you don't have actual social contact with them? If you have Sky and loitered in front of the screen the week before his Simpsons episode aired, you would have developed an almost inevitable Gervais Saturation Point. My problem (or good fortune) is that I know someone who knows him and she's fiery in her defence of the man underlining the fact that it's the act that is the born liar of the inanities. I work hard for my puns and I'm not about to apologise for them now.

The American version of The Office is a big fat hit lining Gervais' considerably deep executive pockets even further. I've not seen a single episode but it has had fairly good press and Evan Almighty aside, Steve Carell has real comic talent but is perhaps too good looking to be taking off any version of the insufferable David Brent. It's fair to say that a show occasionally directed by one of my heroes, Joss Whedon, is worth a look. Just haven't got around to that look yet. I found the BBC original... uh... not my cup of tea. I just wanted to stand there, call Brent an appalling, racist, misogynist cringing shell of a human being and leave through the nearest exit. But then Extras perked me up (not necessarily the celeb cameos) because he created a sympathetic character that really did develop to a degree and his final episode's impassioned plea on Celebrity Big Brother had a touch of authenticity about it.

So let's pass over the smaller Hollywood forays (character actor for hire) – I didn't see Ghost Town – and move straight to an alien planet as fiercely unusual as Cameron's Pandora. I knew the pitch of the movie – Gervais learns to lie in a human society where lying is non-existent, not natural. I rubbed palms together with glee at how visually (this was a movie after all) the film-makers were going to set that world up. After hearing a running commentary of the company credits by Mr. Gervais, I was deflated from moment one. He just tells us the salient facts, bang. No visual style to what is in essence a very talk-based movie. When the title comes up over a shot of Gervais in a hallway I had the immediate and uncomfortable impression of cheapness and British cheapness at that, perhaps cheaper than the American variety. The movie was also lit very flatly which did nothing for me at all. It looks as if the cinematographer was told "It's all in the words..." and given ten minutes per set up. As soon as the word 'masturbate' leaks out from leading lady Jennifer Garner, I thought I'd spotted a small weakness in the overall logic of the world Gervais was inhabiting. When waiters start to come on to patrons presumably honestly, that sealed it. This is not a world in which no one can tell a lie. It's Sunnydale at the time of the extraordinary musical Buffy episode Once More With Feeling.

As mentioned, this is not a world of painful honesty but honesty because of some ridiculous ill-thought-through mania to actually reveal thoughts, which under any normal circumstances, would stay brain-locked. Everyone in The Invention Of Lying blurts out the truth for comic effect but the overall outcome is one of "Why is everyone verbalising their deepest thoughts?" Where's the explanation of the ice slide attached to their minds so no thought is safe from a fast track to the mouth? It comes close to scuppering the movie. A film that does not adhere to its central premise invites detachment. It's the truth, yes but a truth that doesn't necessarily need to be verbalised. It is a mutant strain of destructive DNA in a movie with a concept higher than Michael Bay's hat size. It niggled at me all the way through. "I know you may be thinking that, but why-oh-why are you saying it?" Gervais isn't stupid and he must have encountered this problem in his truth-telling world while co-writing the script. Maybe he thought the movie was funny enough to deflect anyone's logic snapping on. Alas, no. Not by a long shot.

In fact, The Invention Of Lying is more an achingly predictable rom-com than it is an out and out comedy. Only one of several high profile guest stars (and one of my personal favourites), Tina Fey, comes out with any aplomb and even her entire performance is a stream of truthful verbiage that really should live only in her head. But I smiled at her scenes (all too few). Morality is not touched upon in this world because Gervais can stroll in and rob a bank by the simple expedient of the teller not understanding that he can lie (they have no word for it in Bizarro World). The lying continues until a telling moment when Gervais' mother is dying. He comforts her with the heaven schtick (invented on the spot by a desperate man just like the unreal thing) and she dies with a smile on her face. Word gets around and before you know it, Gervais is Brian from the Life Of, a reluctant prophet whose lies have started something. Holed up in his house after upping the quality of his life through outright fraud, robbery and deceit (he's the hero, remember) he has to come up with the same bullshit he told his mother to keep the crowds off his back.

Now this is where Gervais has his cake, eats it, vomits it back up again and serves it anew. A renowned atheist, Gervais now combines the biblical Moses and Jesus and appears with the ten commandments, Gervais style (with mansions) and after significant failure in the wooing Garner department, lets himself go with the result of our Ricky resembling none other than the clichéd appearance of the big J.C. Jesus Christ... I'm reminded that to make it in the US you have to appeal to the majority and the majority are god-fearing Christians. Gervais seemed to go out of his way not only to reassure people that this movie is still respectful of religion despite the pot shots and that in one interview I saw, he even blurts out "It has a happy ending..." This is press junket desperation, the act of a man who so wants to succeed he gives away all his eggs before anyone's even mentioned ordering an omelette.

OK. The Invention Of Lying is not the worst Hollywood movie ever made, it's just a little muddled regarding its core conceit and could have been a lot tighter, more subtle and smart but smart Mr. G. has gone for the mass laugh and the mass dollar. Alas, I think because this outing delivers very few of the former, it simply won't generate buckets of the latter. But what do I know? And that's no lie.