Basically, the game is a glorified version of Snake, with players guiding an ever-growing procession of things around a field either trying to gobble up more things, or avoid dangerous ones, all while not bashing into walls or obstacles. It's something most people have probably played at some point in their life, probably on their mobile phone, but with a shiny veneer of tongue-in-cheek humour. What makes the whole thing work is the ridiculous settings players are thrust into, which includes driving around a camp site running over tents with a tractor, or zipping around London on Saturday as Britain's prime minister while avoiding all of the protests marching around town.
While the missions and their objectives are both very silly, the majority of the laughs comes from all of the comments everyone is making while you drive / walk around a level doing your thing. It largely pokes fun at politics and the socio-economic situation in the UK, and really cuts to the heart of a lot of the problems facing the country. About my only complaint is that they focused so much on David Cameron here when there are so many other people in his party that deserve to be mocked as well. I didn't really notice any jabs being taken at George Osborne or Iain Duncan Smith, and, even more shocking, not a one at Michael Gove. Michael Gove. The man is practically a walking punchline.
From an aesthetic standpoint, NotGTAV is about as lo-fi as they come. The visuals are crayon scribbles with just enough detail to figure out your location and what you're driving. All of the sound effects are sampled mouth noises, and the music is people humming / singing in the background. They even went through the trouble of making mock radio stations for the levels set in London.
The game is dirt cheap at about three bucks regular price, and even less when on sale. It's very short, but benefits from that as the jokes would have worn thin if it was drawn out too much. At its current length, with the satire it has, the game is an entertaining little romp. Like I said before, if you're not from the UK or at least up to speed with the news over there, the majority of the humour will go straight over your head. Those who are will have themselves a good time.
