Another month, another superhero movie. Hollywood has well and truly struck oil with its tales of costumed adventurers and superhuman powers, so it's no surprise that they keep on mining it. Hot on the heels of May's Avengers: Age of Ultron comes Ant-Man, the twelfth instalment in the possibly-neverending Marvel Cinematic Universe. It's the origin story of a hero in a super-suit that can shrink him to the size of an insect... and it's much, much better than that description suggests.

Little was expected of Ant-Man. The film has endured years of complex and laboured development, with the original writer and director replaced and the script radically rewritten well into pre-production. The character himself is, no pun intended, hardly one of the heavyweights of the superhero world, and fans were quietly expecting a film that was somewhere between unremarkable and (thanks to a trailer featuring Thomas the Tank Engine) a bit silly.

Fortunately, it's neither. Instead, against the odds it's a tight, well-scripted action heist film that's in turn funny, emotionally satisfying and genuinely exciting. The lead actors are uniformly excellent too, with Paul Rudd excelling as the loveable rogue in search of redemption, and Michael Douglas giving arguably his most likeable screen performance ever as the story's pivotal inventor genius.

The fact that the film is so good, having been so unfancied, is somewhat fitting in the context of it's own plot. Ant-Man tells the story of Scott Lang (Rudd), a hot-shot engineer who has made heroically bad decisions, and now finds himself recently released from jail and cut off from his young daughter. He's a man desperately in need of redemption, and it's offered to him by Hank Pym (Douglas), the one man who still believes he's capable of greatness. In agreeing, Lang embarks on a David vs Goliath mission to stop a powerful weapon falling into evil hands, and one which will see him learning to operate at minuscule size.

The boy shepherd who fought the giant is an apt metaphor here. As Malcolm Gladwell explained in his book named after the famous Bible story, sometimes the very things that others might count against us as disadvantages, can actually be powerfully used in our favour. Young David was an expert slingshot-operator disguised as a simple shepherd boy; Ant-Man is a seemingly untrained man in an archaic costume who nevertheless possesses true heroism. In being small, David won the upper hand by being under-estimated; by shrinking to tiny size, Ant-Man is able to accomplish the otherwise impossible.

This theme of the underdog earning redemption is just one of several in the film that chime with Christian theology. The relationship between Lang and Pym also echoes the concept of how God sees us not just as we are, but as we could be. And Lang's humility throughout is exemplary; despite having 'good' reasons for the crimes that saw him imprisoned, he demonstrates no bitterness or resentment about them. He accepts that he has 'sinned and fallen short' of the expectations that would allow him a relationship with his daughter; his focus is on winning that relationship back. Lang's example even has a redemptive effect on the group of petty criminals who've become his sidekicks; as the film wears on we sense that they're also choosing a better path at his leading.

Just when you might have expected Marvel to trip up, the mighty superhero franchise has held its running stride impressively. Ant-Man changes the tone slightly, just like Guardians of the Galaxy before it, and successfully continues a now-lengthy line of audience-pleasing hits. Those who expected a Thomas-style derailment will be delighted to discover an entertaining movie, unencumbered by confusing plot lines, and with a heart at the centre that is concept-defyingly huge.

Martin Saunders is a Contributing Editor for Christian Today and the Deputy CEO of Youthscape. You can follow him on Twitter: @martinsaunders