There's just one word to describe what this game is. Amazing. This game is proof that human nature is truly limitless.
At first I was utterly shocked by how big Liberty City was. The time and effort Rockstar put into this is beyond anything I can imagine and honestly something that I don't notice in much games anymore. Then it was the atmosphere you were dropped into. The reality was incredible and just epic. After some hours playing I started to pick up on the smaller stuff that seemed like everyday events though only in real life, not a video game. Such events range from when breaking a car at a low speed you can hear the slight squeaks it makes just before it comes to a complete stop. The overall physics of the driving experience; better than most Need for Speed titles, to be frank. Another thing was when you shot someone, they would react to where you shot them. For instance say you shoot someone in the knee cap, the first thing they would do is keel over. Well expect such animations in GTA:IV. The blood splatter is mercy-less and exactly what should be seen in popular shooters now a days.
Moving onto the story mode. I don't want to give away anything so this will be brief. Dan Houser went all in on this title like he usually does with all the other GTA's he wrote. The back story leads you right into the action. There's an explanation for almost everything. And there is certain parts that let you control the outcome (i.e you have to decide to shoot one of two people). I absolutely recommend buying the Ballad of Gay Tony exp. pack because that story also is incredibly fun.
Lastly, the online mode. I was surprised by this addition and very happy. There is a few different modes that you can do like, TDM, free-for-all, and some objective modes. Though ultimately to have the most fun; grab a few friends, hop online in a free roam room and just blaze it up with whatever rules you want. Find a cop car and do some cop chases. Amazing.
If you love deep stories, than this is perfect for you. The type of stories that keep you involved with many different friends and foes are the best ones. This game will go down as top 3 best game I've ever played. There will be no game that dismantles this. Amazing.