In the book
The Atheist's Guide to Christmas, David Baddiel does a chapter on how there has never been an Atheist movie. He has a point as it is difficult to plot a fictional film, without some kind of 'epiphany' moment and, as this film demonstrates, good stories require imagination and, ultimately, lying.
This film dispenses with the need for a religious epiphany by making the epiphany instead into the discovery of lying and the ability to flatter others. There is also a sub plot where Gervais introduces the idea of eternal life and 'the man in the sky' to the truth loving people of planet Earth, who believe him because no-one has ever told a lie.
On top of this, this film has that rare quality of being an atheist comedy, being as it makes the idea of atheism being the truth into one of the key aspects of its humour.
Of course, there is much more to the film than just a narrow view-point on the world and it only struck me at the end of the film that it had this subtext.
Still, if you want to see a true world first - a movie (not a documentary) that tactfully deals with all things skeptical, then get DVD as it will also teach you why such beliefs will never be popular, no matter how true they are...