It's been more than a year since we last trawled the vast post-apocalyptic wasteland of Fallout 3 and after conquering all that the Washington wastelands has to offer, it's high time for more mutant slaying, wandering exploration and darkly humorous branching dialogue.

Fallout: New Vegas begins with your apparent death, which might not seem like the most promising of starts, but don't worry because even though you've been shot twice in the head(!) and left to rot in a shallow grave out in the Mojave desert, you're soon rescued by Vegas Vic – a mysterious robot – and taken to the kindly Doc Mitchell, who patches you up. This is where our hands-off demo lead by Senior Designer Chris Avellone commences, as your character awakens to the benevolent visage of the good Doc, who has selflessly reassembled your head for you.

This smartly introduces you to the character creation interface as Doc Mitchell makes sure he put everything back in the right place and that you remember your name, which you can input or use the default title of 'Courier' – your character's job role. After this you answer a few questions with the Doc and go through the Vit-O-Matic vigour test to assign your abilities, Then you're good and ready to embark upon a brand new quest, blinking out into the sunlight as you did when you first left Vault 101.

At this point, it's worth noting that New Vegas is a completely new story, with completely new characters and a fresh setting. Yes, it uses the same engine and much of the same assets as Fallout 3 and at this current stage in development it certainly looks no different, but then can you really blame Obsidian for playing it safe? Yes and no. It's perhaps surprising, given that Avellone was the lead designer on cancelled 'could-have-been-Fallout 3' project Van Buren, that Obsidian has decided to plough a familiar, well-worn furrow with New Vegas. Perhaps doing so is the path of least resistance for the developer. And let's not forget that this is a full-sized spin off and not a fully-fledged sequel.

So, upon leaving Doc Mitchell's humble abode, decked out in Vault 21 garb, a Pip-Boy 3000 (obviously) and armed with not very much at all, you venture to Goodsprings – a Wild West flavoured settlement inhabited by the usual menagerie of classic Fallout weirdos and deadbeats. Entering the Prospector Saloon, we first meet Sunny Smiles, who is anything but. After a chat, we go and help her dispatch a few pesky geckos with the 22. Varmint Rifle, which like many of New Vegas' weapons, grants a special combat bonus. This particular rifle does extra damage against limbs, but there's a greater emphasis overall on weapon effects and upgrades, giving you three different attachments to add to each of your guns.

Avellone proceeds to show us a pistol he's augmented with a scope, barrel and larger magazine, and it looks far meaner than its vanilla counterpart. This is preparation for the first main mission, which is to protect a weird guy called Ringo who lurks in the saloon toilets. A fellow called Joe Cobb is causing trouble in the town with a gang of so-called 'powder gangers', so the bar's owner, Trudy, calls upon you to round up a gang to go tackle Cobb and his cronies. After a quick talk with Ringo, Sunny, Chet from the general store and Easy Pete (who also gives us a few sticks of dynamite thanks to a dialogue option unlocked due to our 25 point explosive skill), we're good and ready to tackle the gang. Along the way, our hero gets hold of the game's new 9-iron and enters the trusty VATs mode showing that a press of Y now initiates a specialised weapon specific move, designed to add “spice” to melee combat. This one is called 'Fore!' and is – as you'd expect – a swift, (dis)graceful golf swing to the plums of your targeted victim. Tiger Woods, eat your heart out.

Incidentally, Cobb's head went flying off in classic VATs style outside of VATs, demonstrating the dynamic kill cam which can now be triggered at any moment. Upon completing this mission for the people of Goodsprings and taking out Joe Cobb, we earn the acceptance and trust of the townsfolk. This is part of the new reputation system that has overarching consequences across all of New Vegas, so incurring the wrath of one faction will delight another and vice-versa. So when we betray the loyalty of the New California Republic by activating the Helios One plant's generator to reroute power to the Archimedes II orbital laser, only to rain florescent laser death upon the NCR troops below, they'll remember it and will potentially never trust you ever again. But then again, it is easy to slip past the facility's idiotic custodian, Fantastic (who has a “theoretical degree in physics”), and once you get to the generator, you're presented with a variety of options that have a range of consequences. Remember, just because there's a big space laser at your fingertips, you don't have to use it to kill everyone in the vicinity.

Before our demo finishes, Avellone shows us Primm; a town surrounded by a rollercoaster and home to the besieged Bison Steve Casino; and Novac; a city so-called because the entrance is flanked by a broken 'No Vacancy' sign that reads, well, 'No Vac' obviously. There you'll find a huge motel sign that also happens to be a massive derelict dinosaur-shaped gift shop called Dinky, which doubles as a handy sniper nest. Here you'll also meet ex-NCR member Craig Boone, a crack shot sniper who can join you as a partner.

We meet another partner character, Raul the ghoul later on, in the central Black Mountain location where a mental, aggressive breed of super mutants from previous Fallouts reside. Joining up with him, we take on the band of Nightkin super mutants who have been driven insane by an over exposure to Stealth Boy technology. Using the grenade machinegun – which spits out grenades at an alarming rate – the Nightkins and their cross-dressing, peroxide-wigged leader, Tabitha, soon fall under the duress of so many explosive projectiles that our super mutant killing spree antics are sure to make Raul and the Brotherhood of Steel happy.

There are two breeds of super mutant in New Vegas, the smart kind who can talk and articulate and the self-explanatory 'dumb-dumbs'. As one breed naturally hates the other, you can play them off against one another and sit back and watch as they fight. Fallout: New Vegas reputation system is perhaps the most significant change to the formula, enabling you to orchestrate devious machinations behind the scenes while hopefully maintaining enough favour with the communities and factions that matter.

It might look like Fallout 3 with bluer skies (the bombs didn't fall as hard on New Vegas' townships and settlements) and few, if any visual additions, but it's the subtle differences that should make it worth revisiting Fallout. A smattering of old creatures and familiar names from previous Fallout titles will delight the purists, and the optional hardcore mode (complete with achievement for completion) with ammo weight, slow-effect stimpaks and a demand on gathering water to avoid dehydration will satisfy Fallout 3 veterans thirsting for a challenge. Simply put, if you liked Fallout 3, it's highly likely that you'll love New Vegas.

Fallout: New Vegas is hitting the wastes this autumn 2010.