Rockstar doesn't do things by halves. GTA IV set the standard for living, breathing game worlds and now the first expansion raises the bar for downloadable content - to the extent that it almost redefines the term.
This isn't a simple array of new weapons or missions, it's a massive chunk of extra stuff - new missions, new weapons, new vehicles, new radio ads, new music, new everything. It's hours of extra material, and brings an experience surprisingly different to that of the original game.
It's delivered through a new storyline based around Johnny Klebitz, second-in-command of fading biker gang The Lost, and the escalating tensions between him and fresh-from-rehab boss Billy. The bulk of the new content remains biker-themed, with new gang-based modes in single and multiplayer and a clear focus on big, explosive, swearing-filled shootouts rather than the gentler, more varied adventures of Niko Bellic. Even the radio station updates are biker-based, with former metal frontman Max Calvera joing Iggy Pop on DJ duty plus the likes of Motley Crue and, er, Rod Stewart added to the playlist.
The social side is updated too, with the newer and manlier option of riding out with your brothers (on bikes which are much easier to stay on, by the by) and brining the pain to your many enemies. En route to a mission you can hold a certain spot in formation to trigger conversations that provide story details and built up your relationship with people, and if everybody survives the massive firefight that inevitably results when you arrive then their skills improve.
If you crave something deeper there's still the option to call up your buddies and do some new hard-rockin' things with them, like air hockey or arm wrestling - the latter requiring so much abuse of the right analogue stick it's almost as draining as the real thing. Most usefully, you can ring up for instant bike delivery, new weapons (nearly of which are hugely powerful and hugely entertaining, like the car-munching sawn-off shotgun) or a couple of helpers for your latest fight. It's a surprisingly significant change from Niko's solo slog, and while the structure of the missions doesn't change dramatically (chase this person, retrieve this item, kill this gang) the fact that you have to do everything in a team sparks a genuine sense of unity.
It serves as a background for a simpler, coarser, more action-packed narrative. While there are still some grand themes of brotherhood and loyalty ticking away underneath, they're realized in explosive style that'll play well with those who found Niko's crime drama too worthy. Rare is the mission that doesn't end in a pitched gunfight with your gang facing off against rivals the Angels of Death, the police, or some other group of heavily armed foes, and new arrival the grenade launcher gets a lot of use. GTA staple, the on-rails chase, makes a cracking reappearance and there are some welcome new tweaks - most blessed are mid-mission checkpoints for easier retrying.
It's also incredibly well integrated with the main storyline of GTA IV, starting with a glimpse of Niko in the opening cutscene. This is no a bolt-on sidequest; it feels like something that was planned from the start, and the storylines and characters are constantly meeting. Niko makes only a few brief appearances, but the consequences keep on coming as characters are story arcs are passed on to or killed off by him, while his are ended by yours. The criminal underworld of Liberty City is a huge and sprawling thing, and it's fascinating to see how Johnny's path crosses the one you've already taken with Niko - albeit avoiding the parts where certain characters might or might not have been killed off.