Stepping off a boat in the shoes of illegal immigrant Niko Bellic as he arrives in Liberty City at the start of Grand Theft Auto IV, you can tell immediately that Rockstar North's latest offering is something quite special. Yes, this is another GTA game in which you'll likely spend the bulk of your time stealing cars and gunning down cops and criminals, but it's also much more than that. GTAIV is a game with a compelling and nonlinear storyline, a great protagonist who you can't help but like, and a plethora of online multiplayer features in addition to its lengthy story mode. The PC version adds a customizable radio station and a video editor to the package, and also ups the multiplayer count from 16 to 32 players. It's not all good news, though; the game suffers from some noticeable performance issues even on rigs that far exceed the unreasonably high recommended system specifications, and you need to be signed in to Windows Live to save your progress in the single-player game. This should have been the best GTA game yet, but it's inferior to its console counterparts.

Liberty City has changed a lot since 2001.

One of the many things that set GTAIV apart from its predecessors is Liberty City, which is more convincing as a living, breathing urban environment than anything you've seen in a game before, and which bears little resemblance to its namesake in 2001's GTAIII. Liberty's diverse population believably attempts to go about its daily business, seemingly unaware that several criminal factions are at war in the city. Niko has no such luck. He's compelled to start working for one of the factions shortly after arriving, when he learns that his cousin Roman has some potentially fatal gambling debts. Niko's military experience makes him a useful freelancer for employers in the business of killing, and though his reluctance to carry out their orders is often apparent, he does whatever is asked of him in the hope that completing missions for other people will ultimately give him the means to complete his own.

But Niko doesn't have to do everything that's asked of him. On several occasions as you play through his story, you'll be presented with decisions that afford you the option of doing what you think is right rather than blindly following instructions. You don't necessarily have to kill a target if he or she promises to disappear, but you have to weigh the risk of your employer finding out against the possibility that the person whose life you spare might prove useful later in the game, or even have work for you in the form of bonus missions. To say anything more specific on this subject would be to risk spoiling one of GTAIV's most interesting new features, but suffice it to say that every decision you make has consequences, and you'll likely want to play through the game at least twice to see how the alternatives unfold.

Grand Theft Auto IV's story mode can be beaten in less than 30 hours, and there are so many optional activities and side missions to take part in along the way that you can comfortably double that number if you're in no hurry. The majority of the story missions task you with making deliveries and/or killing people, and play out in much the same way as those in previous games. With that said, most of the missions are a lot easier this time around, partly because Niko is a more agile and efficient killer than any of his predecessors, and partly because the LCPD seemingly has better things to do than hunt down an illegal immigrant who's gunning down undesirables all over the city. Some of the more imaginative missions sprinkled throughout the story include a kidnapping, a bank heist, and a job interview. The cinematic cutscenes associated with story missions are superbly presented and are the sequences in which the game's characters really shine. Without exception, the characters you encounter benefit from great animation, great voice work, and superbly expressive faces. They're not always so impressive when they join you on a mission and refuse to do what they're supposed to (for example, not following you on an escort mission, or failing to negotiate a doorway). Nevertheless, these problems are few and far between, and they're made less painful by the new "replay mission" option that you're presented with whenever you fail.

He's a gun for hire, but Niko Bellic is the most likeable GTA protagonist to date.

New abilities in Niko's arsenal include scaling fences and walls anywhere he can get a foothold, shimmying along ledges, and, most importantly, taking cover behind objects. The ability to stick close to walls, parked cars, and the like at the touch of a button makes GTAIV's gunplay a huge improvement over that in previous games, and, in tandem with the new targeting system, it also makes it a lot easier. Enemies are rarely smart enough to get to you while you're in cover, and given that you can lock your targeting reticle on to them even when they're hidden, all you have to do is wait for them to poke their heads out and then pick them off with a minimum of effort. Locking on to enemies targets their torso by default, but you can use the right analog stick to fine-tune your aim and kill them more quickly with a headshot or two. Playing without using the lock-on feature is viable if you're using a mouse and keyboard, but makes things more difficult on the Xbox 360 controller. You'll need to master the technique at some point, though, so that you can shoot blindly at enemies from positions of cover when you dare not poke your own head out to line up the shot.

Given the amount of trouble that you get into as you play through the story mode, it's inevitable that the police are going to get involved from time to time, even when their presence isn't a scripted feature of your mission. Liberty City's boys in blue are quick to respond when you get flagged with a wanted level of between one and six stars, but they're not nearly as tough to deal with as their counterparts in previous GTA games. They don't drive as quickly when pursuing you, they rarely bother to set up roadblocks, and you'll need to blow up practically an entire city block before the FIB (that's not a typo) show up. Furthermore, you're given an unfair advantage in the form of your GPS system; when you're not using it to plot a valid route to any waypoint of your choosing, it doubles as a kind of police scanner. Any time you have a brush with the law, the GPS shows you the exact locations of patrol cars and cops on foot in your area, and highlights the circular area (centered on your last-known whereabouts) where they're concentrating their search. To escape, all you need to do is move outside the circle and then avoid being seen for 10 seconds or so, which is often best achieved by finding a safe spot and just sitting there. It's not a bad system in theory, but in practice it makes dodging the law a little too easy, especially when your wanted level is low and the search area is small.

When you're not running missions for criminals, taking part in street races, stealing cars to order, or randomly causing trouble, you'll find that there are plenty of opportunities to unwind in Liberty City. Some of these optional activities offer tangible rewards that can prove useful in missions later on, whereas others are just a fun way to kill time and take in more of GTAIV's superb humor. For example, you can watch television, listen to numerous radio stations, check out some genuinely funny shows (including some big-name acts) at cabaret and comedy clubs, and use a computer to surf the in-game Internet.

In case you were in any doubt as to how the series got its name.

GTAIV's Internet is filled with spoofs of all the kinds of Web sites that you'd only ever look at accidentally or when you know there's no danger of getting caught. Some of them can be found only by clicking on links in spam e-mails, whereas others are advertised prominently on the search page. There's plenty of amusing stuff to find if you spend some time in one of the "TW@" Internet cafes, but the most interesting site by far is an online dating agency through which you can meet women who, if they like your profile, will agree to go on dates with you. Dating and socializing with friends is something you can spend as much or as little of your time doing as you like, and though the people you meet can occasionally be demanding to the point that they become irritating, keeping them happy invariably benefits you in some way.

Keeping friends and dates happy means spending time with them and doing things that they enjoy, and all of them have different personalities. Some friends like to join you for minigames such as tenpin bowling, pool, or darts, whereas others prefer to go out for a meal, get drunk, or take in a show. Of course, dates are much fussier than regular friends, and their opinions of you are influenced not only by whether you pick them up on time, where you take them, and whether you try your luck when dropping them at home, but also by a number of much more subtle factors. Dates will comment on things like the car you drive, how you drive it, and the clothes you wear. They'll even notice if you wear the same outfit two dates in a row, though not all of them will be bothered by it. The rewards that you get when another character likes you enough vary depending on who it is. Without wishing to give away specifics, befriending a lawyer can prove useful if you're having trouble with the cops, for example, and having a nurse on your friends list can literally be a lifesaver.