Borderlands 2 is takes everything that worked about Borderlands, and turns it up to 11.
We're still on Pandora, where the Vault Hunters of the first game are now spearheading a resistance against the new evil - mask wearing Handsome Jack - and recruit new PCs to assist them. You have a choice of four classes to play with out of the box (although another was given away for pre-orders and another has been released as DLC), some fairly similar to the earlier games, others more markedly different. As the plot unfurls, the gameplay is more RPG than shooter, picking up lists of quests from progressive hubs before moving onwards, levelling up and collecting loot from rewards, drops and chests.
Married to this compulsive loot-hoovering are solid shooter mechanics featuring what are now pretty standard features like regenerating shields and limited weapon slots. The UI is hugely improved over the dreadful one that came with Borderlands, although it still feels designed for consoles and is needlessly clunky on the PC. Vehicles, something that Borderlands seems to get better at as it's DLC rolled out, seem to play a better part, with the sprawling levels making them a necessity, unless you're a big fan of running everywhere.
But mostly, it's just more. More crazy redneck psychopath midgets with spikey guns. More aggressively dangerous wildlife. More amusingly voiced NPCs giving you morally dubious quests to steal something or blow something up, or kill someone. More everything. More fun. And thats the thing; Borderlands 2, like Borderlands before it, is fun. Tons of fun. Fun without the niggles and quirks that occasionally popped up in it's predecessor, it's just a madcap whirl of guns and silly accents and exploding stuff.
And more than that, it's huge. Out of the box we must have got over 25 hours of gameplay out of a single playthough, and everytime we thought "this must be near the end" another zone and another series of quests opened up in front of us. And on top of that, it changed up often enough that we never felt padded, or strung out, or bored of a particular environment. Borderlands 2 is just a blast, start to finish, and well worth picking up if you've any patience for shooters at all.