The past 10 days have been very busy for me. I've broken into countless military bases, taken vast quantities of drugs, and have shot several hundred people in the head. I've stolen the Declaration of Independence. I've moonlighted as a contract killer. I've helped to run a warped presidential election. I've even gotten really sick after drinking from a toilet bowl. But enough about my holiday trip to Skegness - let's talk about one of the biggest releases of 2008.

Fallout 3 is a massive, massive game. This magnitude exists on a number of levels: for a start, there's the game world itself - a scarred post-nuclear Washington, packed with decrepit survivors, mutant beasties and marauding raiders. Then there's the enormous degree of change since the last game - a shift of developer and a move into full 3D graphics. There's the huge degree of anticipation, both from enthusiastic newcomers and from the more sceptical Fallout hardcore. It's probably due to a combination of all these factors, but for whatever reason Fallout 3 feels like the biggest game I've played all year - so much so that I've already run out of synonyms for the word 'big'. And despite a number of flaws, it's also one of the best games of the year too.

For the benefit of the uninitiated, here's a quick recap of the backstory to the Fallout universe: In the year 2077, World War III turns most of the Earth into a giant nuclear ashtray. A small percentage of the US population survive the conflict by fleeing into Vaults - giant underground shelters built by the VaultTec corporation. The first Fallout placed you in the skin of a jumpsuited resident of Vault 13; when your water purification chip breaks, you are chosen to set out in pursuit of a new one - braving the wasteland of post-apocalypse California. After a remarkably downbeat ending to your adventures, your Vault Dwellers set off to found a small village of their own. Fallout 2 cast you as a grandchild to the first protagonist, offering a much larger play area and a greater variety of distractions from your quest to find a GECK - a powerful piece of technology with the power to save your dying tribe.

Fallout 3, set some 36 years after its predecessor, shifts its focus to the East coast of America - to the claustrophobic confines of Vault 101. The game begins with your birth, generating your character's gender, name and appearance. After this you'll spend about 20 minutes speeding through your childhood and adolescence via a neat quest designed to introduce most of the game's key concepts and mechanics - including the much-discussed VATS combat system. At the end of this brief introduction your rebellious father disappears; his sudden departure enrages the vault authorities and causes a minor riot - leaving you with no choice but to follow him. You emerge from the underground, your vision blurring under a sun you have never seen before - and then you set out across the Washington wastelands.

You start in the vault but don't stay there for long

What follows is really up to you - in the short term, at least. You'll be given a pointer about where to look for your Dad first, but the world is more or less your oyster. Since this is an RPG, your main priority should be to get some experience and to start levelling up. The area immediately surrounding Vault 101 isn't too lethal, but if you immediately head to the far corners of the map you'll swiftly find yourself in trouble. Bethesda has largely abandoned the mechanic used in Oblivion which scaled random enemies to match your capabilities - so if you go wandering off into a dangerous area, you're bound to come a cropper. As a result of this design choice, the wasteland immediately feels a threatening place - something further compounded by the devastated scenery that surrounds you in every direction, thanks to a rather spiffy draw distance.

As you might imagine, the thermonuclear apocalypse has had a detrimental effect upon public transport - so you'll be doing all your exploration on foot. In all likelihood, you'll be viewing proceedings from a first person perspective - a third-person option does exist, but most people are likely to get fed up with the slightly floaty way your hero moves. Either way, you'll soon find that the landscape itself is the star of the show. Bethesda have done an amazing job in creating a ruined environment: from burnt-out towns and twisted highways to the looming metropolis of downtown DC, the in-game scenery drips with a tragic, ruined atmosphere. This is probably just as well, since it takes a fairly long time to walk from point A to point B. On the plus side, once you've discovered a given location, you'll be able to instantly fast-travel back there at any point you wish. To be honest, I was initially fairly uncertain about whether or not I thought this was a good idea: It's certainly a convenient feature, but its not a particularly realistic one - and for a while I was concerned that it would dilute the dangerous atmosphere of the wasteland itself.

VATS works really well in combination with real-time combat

After spending a decent length of time with the game, I've come to the conclusion that this slightly odd warping is simply a necessary evil. You'll end up doing an awful lot of to-ing an fro-ing in Fallout 3 and if you had to do every journey on foot, you'd probably get very bored. As weird as it may seem, the warping mechanism allows you to set up camp somewhere - probably the house that can be acquired early on - and once you get into the habit of periodically returning to your base, you'll find that you start thinking a bit more tactically about the weapons and kit you'll need for the road ahead. At low character levels you'll probably spend a fair bit of time looting corpses and lugging your treasures back to the nearest merchant, so it's often handy to travel light.

On all but the shortest of journeys, you're bound to run into some form of enemy. Combat is conducted via a mixture of real time shooting or fighting, and targeted attacks made using the VATS system, which pauses the action and allows you to queue up a limited number of actions. You're probably sick of hearing about this by now, but it's worth confirming one more time that the whole stop-start thing works really well: it lends a tactical edge to battles, but it doesn't slow things down too much at all. Fighting outside of VATS takes a little getting used to: while it may look and feel as though you're playing a FPS, attacks are calculated along the lines of standard RPG rules. In other words, unloading a clip into a bandit's leg won't automatically cripple them unless you score a critical hit. It's a strange hybrid of action and strategy, but it's highly satisfying once you get used to it - and for some strange reason you'll never get tired of watching the slow-motion deaths of your enemies.

In terms of the weapons at your disposal, there are five skill classes available - small, large and energy-based firearms, plus a selection of melee and hand-to-hand weapons. To be honest, the former fair distinctly better than the latter: from super-mutants to hard-nailed mercs, most of the antagonists in Fallout 3 have some form of ranged attack, so you're far better off wielding some form of gun. You'll also find that close-range swipes and punches look a bit weird - the character models don't always connect as well as they might. In any case, the guns simply sound better: the magnums boom and the rocket launchers whoosh - and during a VATS kill these noises are slowed and distorted to excellent effect. While we're on the subject of killing, we have to flag up our love for the sloppy way that enemies melt into the ground when you hit them with a plasma rifle. It's gruesome, funny and very reminiscent of the old-school Fallout death animation.

Another favourable comparison between Bethesda's sequel and its Interplay counterparts is to be found in the way skills are used. As you level up through experience, you'll be given points to spend on improving your abilities. Aside from combat, you'll be able to improve your training in areas such as medicine, science and speech. While boosting any of these has a benefit in its own right, you'll also find that raising certain skills will unlock new dialogue options when conversing with NPCs, opening up alternative ways to complete quests. Such moments are highly pleasing, since they reward you for growing your hero in a particular way and make you feel connected to the character you've built up - which is surely half the point of playing a role-playing game in the first place.

The weapons are mostly excellent

Indeed, I'd go so far as to say that the overall quest design in Fallout 3 is one of the game's strongest elements. In the early stages you'll find most quests to be relatively straightforward, but once you get stronger and travel a bit further afield, there's all sorts of stuff to be done: one minute you're raiding the National Archives; the next you're a private detective, attempting to locate an android who looks identical to human beings. This last quest, a clear nod to Ridley Scott's Blade Runner, is a perfect example of the way in which players are allowed to follow their own morality. Finding the missing robot is a task of itself since he's undergone facial surgery and has had his mind wiped - and then once you finally find him, what should you do? Do you inform his master, or do you kill the master and let the machine live in peace? But then again, the android no longer knows he's an android - so perhaps you should tell him what he is? It's up to you to decide.

This open approach to morality is more prevalent in some quests than in others, but there's always several ways to approach the task in hand - and you're frequently rewarded for thinking outside of the box. One quest will send you on a mission to assassinate four characters across the world - but if you do a bit of digging around, perhaps you might be able to work out why your employer wants them dead. If you play your cards right, you'll discover what it is they really want. To say much more would be to spoil one of Fallout 3's better adventures - but let's just say that seeing the full extent of this quest will take you several hours. You could just go ahead and do the hits if you're a cold-blooded sort, but if you're the curious type... well, I'll let you see for yourselves.

The main quest in Fallout 3 can be ploughed through in about 30 hours or so, but the chances are that it'll take you much longer. Indeed, if you complete the game in this length of time then you're almost certainly playing it too quickly. Most people will take far longer - if only for the fact that it's so easy to get distracted by things. There are so many places to visit and things to do - and it seems that every time you head out to accomplish one thing, you find three others you'll want to do later. Once it grabs you, Fallout 3 is one of those games that gets into your head and lays eggs. You'll be at work, or on a bus somewhere, and you'll find yourself meticulously planning where you'll go and what you'll do when you next boot up the game. When you finally do rush home and play, you'll find that time whisks by - it's 2am, and you've still not explored that old military base you saw. So you keep on playing, and find yourself zombified at work the next day. Not that this will stop you from making further plans - or returning to the wastes that very same evening.

Enemies are varied, but there are some unwelcome additions.

As you can probably gather, I like Fallout 3 a hell of a lot - and as a long-time fan of the Fallout series, I had my fair share of reservations about the way this game could have turned out. There are, however, a few problems that need to be mentioned. The biggest single problem is the scriptwriting, which varies in quality throughout the whole venture. Most of the time it's fine, but every once in a while you'll hit upon something that's wincingly overblown, or else simply not appropriate for a Mad Max-style wilderness. The worst offenders here are the Brotherhood of Steel - the guys in power armour who dominate the game's artwork. In previous Fallout adventures, the Brotherhood were a group of isolationist, technology-obsessed knights who looked after themselves and pretty much ignored everyone else; they helped you out when they had to, but only when it served their own interests. Here they've become shining protectors of the downtrodden. That's not such a terrible shift, but their righteous pseudo-Jedi dialogue is really quite cringeworthy. "Steel be with you!" cries the guard to the Pentagon, with apparent sincerity.

Bethesda's attitude to radiation is also a little unbalanced. The melancholic tone of Washington's ruins and the ramshackle depiction of the few human settlements are bang on the money as far as Fallout tone goes - so why ruin that by including a weapon that fires miniature nukes? Firing one of these babies will wipe out an entire room - but you'll be fine to loot the bodies two seconds later, since they only leave a tiny amount of radioactive fallout. On a similar level, the studio does a pretty good job of depicting ghouls - the poor mutant survivors of WWIII who now resemble zombies - as put-upon victims, rejected by society. Again, this was a trait of the previous games - so why deflate that by including "feral ghouls" who act like the zombies from 28 Days Later? Don't even get me started on the character who can mysteriously turn into a ghoul in the space of a few hours, if you're mean enough to nuke Megaton - the town built over an unexploded bomb.

These instances of Bethesda dropping the ball are certainly irritating, but the truth is that they will only really hurt hardcore Fallout fans. The use of the word "only" in that last sentence will probably put a few noses out of joint, but it's true: most people who play this won't care a bit - because they never played the original games in the first place. That will be of scant consolation to those of you unhappy with the direction Bethesda has taken, but perhaps you'll take comfort in the fact that the original classics are surely bound to receive new attention in the months following Fallout 3's release. Personally, I'm having a ball with this game. I've been playing it pretty much non-stop since our review copy arrived at the office, but I'm sure as hell not going to stop any time soon. There are elements here that are significantly altered from the first games - some pleasant, some not - but I ultimately find the game to be a good thing: it's a different experience, yet one with many familiar ingredients.

Some quirky dialogue jars with the rest of the game

And for the rest of you... well, you have a treat on your hands. As I said up at the top, this is a massive game: in a month that's seen the release of five or six of the year's best titles, I reckon this is the absolute peach. It's packed with interesting places, with choices to make, with that nebulous sense of adventure you only find in the best RPGs. And after a long wait, it's finally here.