Percy Jackson isn’t just a demigod: he’s one of the great success stories of contemporary children’s fiction. As the lead character of a series of books by the author Rick Riordan about a group of teens descended from the gods of Greek myth, Jackson has helped to kick-start an entire media franchise. His adventures – known as the Camp Half-Blood Chronicles – have sold millions of copies, generated spin-off games, graphic novels and movies, while a TV series is now also on the way.

Their success, most critics agree, boils down to a winning formula. Riordan creates fast-paced, action-heavy adventures that involve an almost video game-like romp through increasingly obscure bits of ancient mythology. They’re irreverent, exciting, and crucially, full of fearsome monsters.

But rather like their teenage demigod protagonists, is it possible that there is more to these stories than meets the eye? According to one new analysis, simply to view the Percy Jackson novels as cartoonish capers through ancient folklore may be to underestimate their impact. In taking out mythical monsters, Percy and his companions are also taking on myths that encumber the real world: about the nature of heroism, leadership – perhaps alpha male-ism itself.

The evaluation, by the Cambridge academic, Frances Foster, focuses on the relationship between Percy Jackson and Hercules; arguably the greatest superhero of all time, who also appears in the novels.

It is a contribution to the much larger Hercules Project, led by Professor Emma Stafford at the University of Leeds, which is examining Hercules’ enduring appeal, from the end of antiquity to the present day. Thanks to centuries of depiction across art, literature, cartoons, TV shows and film, Hercules is a rare example of an ancient character most people still recognise. He influences ideas about body image, politics, and military power. He has also become the blueprint for numerous efforts to create impressions of strength - from Arnold Schwarzenegger to Vladimir Putin.

His treatment in Percy Jackson, however, is highly unconventional. From monster-slayer, Riordan turns Hercules, Foster suggests, into a monster in his own right: a very unusual way to restyle this widely-revered Greek god and demigod. Her study asks the obvious question: Why?

Foster teaches at the Faculty of Education, University of Cambridge, and is a member of its Centre for Research in Children’s Literature. Her research examines how people read and respond to ideas from the ancient world.

“In children’s literature, quite a lot of my work involves spotting something unusual, taking it apart, and trying to understand what’s going on,” she said. “The treatment of Hercules in Percy Jackson is a case in point. One of the main reasons for the novels’ popularity is that they’re easy to read and action-packed, but the way they treat Hercules highlights the fact that there’s actually quite a lot more going on.”

Uninitiated readers may be tempted to see Percy Jackson as a sort of Hercules Mark Two. Like the ancient hero, Riordan’s creation has to complete multiple quests, slay improbable numbers of monsters, and revisit most of the famous 12 labours of Hercules – as well as other Herculean adventures.

Read on, however, and the characters soon diverge. In fact, Foster thinks that the adventures encourage fans to “reassess their impression of what makes a demigod heroic” as Percy encounters the ‘truth’ about Hercules.

For example, the adventures create a backstory for Hercules featuring Percy’s companion, Zoe, who it turns out helped Hercules with many of his most famous challenges, but whom he then wrote out of his own PR. And when the teenage demigods finally encounter Hercules, they find him palpably unheroic: unable to control his desires and grudges. As one of the demigods concludes, he turns out to be less a hero, more ‘a bitter, selfish jerk’.

Eventually, Hercules becomes just another obstacle they have to overcome. “His qualities make him monstrous rather than heroic,” Foster writes. “Hercules is ultimately not a hero to be emulated – just another monster they have to defeat.”

She argues that Riordan is not just doing this to be iconoclastic. By placing his ‘modern’ demigod teen heroes in situations that Hercules himself encountered, he is drawing favourable contrasts with some of the more questionable values that many depictions of Hercules have fed into wider culture.

For example, during the stories, the demigods use teamwork to defeat monsters like the Nemean Lion or Stymphalian Birds: antagonists that Hercules originally defeated by working alone. Similarly, while Hercules famously cleaned out the Augean stables by diverting an entire river to run through them, Riordan forces Jackson to seek an alternative after his attention is drawn to the environmental impact of discharging huge amounts of animal waste into a river.

Foster argues that this is a deliberate juxtaposition: between the ‘monstrous’ heroism of Hercules and the ‘modern’ heroism of Riordan’s demigods. “Unlike Hercules, they work together and care about the consequences of what they do,” she said. “That’s very different to ancient heroes, who tend to operate alone and generate collateral damage for which they never account. Think of Odysseus. He sets off on his voyages with 12 ships, each with a crew of 60. He comes back with precisely none.”

How far the subtleties of Riordan’s reworking of the great archetypes of wider culture have influenced the 11 to 14-year-old audience at whom his books are aimed is an open question. But Foster believes that the impact may be greater than we might instinctively assume.

“There has been some research on Percy Jackson that suggests readers pick up more from it that people think,” she added. “It may be worth studying how far the books do influence their perceptions about heroism or leadership, which often have their roots in the mythology covered by the novels. But we certainly shouldn’t jump to conclusions about what readers are thinking until we have asked them.”

Frances Foster’s study, Demigod, God, or Monster? Rick Riordan’s Hercules, appears in The Modern Hercules, edited by Emma Stafford and Alastair Blanshard, published as part of the Hercules Project.