It would have been easy for Avengers: Age of Ultron – the sequel to Marvel’s franchise mega-hit Avengers Assemble – to rest on its laurels. Thankfully, Avengers 2.0 improves on its predecessor on many fronts even if it doesn’t fully recapture the magic of the 2012 endeavour.

Whereas it took a little while for Avengers Assemble to get going, the opposite is true for the sequel. We begin with a Bond-esque opening skirmish between our heroes and HYDRA cronies that ends with the recovery of Loki’s scepter and a party to remember. But when Tony Stark (Robert Downey Jr.) and Bruce Banner (Mark Ruffalo) attempt to use the power of the scepter to jumpstart a peacekeeping program, the inadvertent result is Ultron (James Spader), a highly intelligent robot hell-bent on human extinction. Making matters worse, Ultron joins forces with powerful Maximoff twins Quicksilver (Aaron Taylor-Johnson) and Scarlet Witch (Elizabeth Olsen).

First and foremost, Avengers: Age of Ultron is an incredible feat of storytelling by writer-director Joss Whedon. In addition to the already sizable assortment of characters there are at least four more significant players introduced, each of whom need arcs that make sense within the context of the story. That makes for a lot of spinning plates, but Whedon and editors Jeffrey Ford and Lisa Lassek pull off an impressive juggling act that keeps the narrative coherent, while giving most of the characters their due.

It’s no secret that Whedon wanted Ultron as the villain for Avengers 2.0 as early as the first Avengers film, and he is superbly realised here thanks to the above reproach CGI and Spader’s chilling vocal performance. Easily the snarkiest robot to grace cinema screens, Ultron is satisfyingly complex, and the juxtaposition with Vision (Paul Bettany, making his first on-screen appearance in the franchise and slotting in to the ensemble perfectly) is just one example of the brainier, more emotive material at play here.

As for the good guys, in a great turnabout from the last film it’s Jeremy Renner’s Hawkeye who gets the biggest dose of introspection and the best dialogue to boot. His subplot gives the film a lot of heart while deftly answering any lingering doubts in regards to the importance of his role on a team that consists of a God, a super-soldier, an all-powerful rage monster and a technological genius.

Speaking of those aforementioned Avengers, we learn a little more about Thor, Captain America and Black Widow thanks to some smart usage of Scarlet Witch’s reality warping powers, with Widow’s back-story proving especially intriguing. It’s little wonder why questions about a solo movie persist. Her burgeoning romance with Banner is another surprisingly clever idea that Whedon gets a lot of mileage out of – helped by the easy chemistry between Scarlett Johansson and Ruffalo – and the human moments between these and other characters are pleasingly effective.

Of course there are an ample amount of superhuman moments too, and Age of Ultron utterly obliterates the already high bar that Marvel themselves set for superhero action. Remember that moment when Iron Man deflected his repulsors off Captain America’s shield? The combos this time round are more plentiful and memorable. Loved Iron Man vs. Thor? The much-anticipated Hulk vs Hulkbuster sequence dwarfs it. Still, it’s perhaps the cumulative power that comes from seeing Earth’s mightiest heroes on screen fighting off numerous foes at the same time that will linger in audience’s minds once the credits roll. Through it all, Whedon’s penchant for highlighting the absurdity of a situation while keeping the tone exactly where it needs to be impresses.

The film is not without its flaws. Even more so than its predecessor, the Whedonisms come thick and fast in Age of Ultron, and there are a couple jokes which don’t quite land. Meanwhile, though Brian Tyler’s score brilliantly incorporates his own Iron Man 3 and Thor: The Dark World themes in addition to Alan Silvestri’s memorable motif, his own new Avengers theme gets lost in the shuffle – and if we’re getting really nit-picky, the climactic fight against Ultron’s army essentially boils down to Avengers vs. cannon fodder. Again.

But it’s easier to ignore the flaws when a film is this much fun, and though Avengers: Age of Ultron is not the best film in Marvel’s ever expanding cinematic universe, it’s undoubtedly one of its most entertaining.