Well, it's not supposed to be yet but across North America many stores have chosen to start selling copies of the game a little early. There are already a few screenshots flying around online. It looks so much better than the PS2 version.
And whatsmore you even get a free novella with the game which if you're like me and love any GTA merchandise is a must have. If you haven't ordered a copy already you can do so by visiting the links to reputable online retailer Amazon.
If you don't want to buy from Amazon and you live in the UK or Europe you can actually get it cheaper at Play.com. The PC version is only £24.99 there. Go buy it!