Three decades have passed since Hollywood last treated us to a movie based on Greek Mythology in all its supernatural splendour. That was the original Clash of the Titans (1981) of course, and although we've had Wolfgang Petersen's Troy (2004) in that time, almost all of the Iliad's supernatural themes were removed from that adaptation. Well, the 29 year drought is about to break with two movies, a remake of Clash of the Titans due out in March, and Percy Jackson & The Olympians: The Lightning Thief, out on 12 February.

The Lightning Thief is adapted from Rick Riordan's 2005 New York Times best-seller, The Lightning Thief: Percy Jackson & the Olympians, a contemporary American fantasy about twelve year old Percy Jackson, an unremarkable child, struggling with school and diagnosed with dyslexia and Attention Deficit Hyperactive Disorder (ADHD). Unremarkable that is until he learns his father is Poseidon, God of the Sea.

The first of five books in a series there's little doubt that Fox 2000 Pictures is looking to fill the void that will be left when the final Harry Potter movie fades from our screens next year. It's notable that Chris Columbus, the man responsible for kicking-off the Potter movies with The Philosopher's Stone (The Sorcerer's Stone for American audiences) and The Chamber of Secrets, is at the helm of The Lightning Thief. Columbus was attracted to The Lightning Thief for its originality, he explains, "I think Rick Riordan tapped into something quite unique, juxtaposing the world of the ancient Greeks with the underbelly of contemporary America."

"To me, this story was perfect because it had this whole great world of Greek Mythology populated by Greek monsters that we could create and design and put in our world," says Columbus. "And, the heart of the story is about a young man who wants to save his mother and find out who his father is. So that made it a very emotional story. The kind of story I respond to as a director."

In this first instalment of what will no doubt become a Percy Jackson franchise, Zeus accuses Percy of stealing his greatest weapon, the Lightning Bolt, and if it's not returned, war between Zeus and Percy's father, Poseidon, will erupt and destroy the world. In one moment the unremarkable boy discovers not only that he's the son of a god but he's a marked boy, wanted by Zeus and other, far darker powers. Fleeing to Camp Half Blood, a training camp for demigods, he discovers that his good friend Grover is in fact his protector and a Satyr (half-goat) in disguise, and he meets Annabeth, daughter of Athena. He also learns that his mother has been captured by Hades, God of the Underworld, who offers her in exchange for the weapon. With Grover and Annabeth, Percy sets out on a transcontinental adventure to rescue his mother and save the day.

Fans of the novels are probably already aware that Percy Jackson in the movie is five years older than his written counterpart. Screenwriter Craig Titley explains the reason for the change, "In the book, he was twelve years old. It was just much more fun to make him seventeen. With that age, we could play with Percy and Annabeth and their relationship." Just as likely, the Studio wanted to set their hero apart from young Harry Potter when we first meet him (comparisons are inevitably drawn between the two series about the magical boys). But I suspect the main reason for the change was the desire to attract the ready-made audience of young adults who have grown up with Harry Potter and who will more easily identify with a seventeen year old than a twelve year old. Where Harry ends, Percy begins.

Increasing Percy's age was a poor decision creatively, and many of the movie's problems stem from it. Some effort has been made to make the relationships more adult, or at least appealing to teens, and the violence and horror is intensified, but this cannot disguise the fact that the story was written with a twelve year old in mind, not a young adult.

As happens so often when adapting a fantasy novel for the screen, the logical implications of introducing change, such as aging Percy by five years, aren't thought through: Percy Jackson is a seventeen year old High School student who can't read English. How has he even managed to make it to High School? Why is he even attending an English Literature class when we meet him? And why is Percy the only demigod of his age who is not already aware of his heritage, as are all the other demigods at Camp Half Blood? The answer of course is that Riordan wrote his story with a twelve year old in mind. And while we're on a roll, why would Zeus suspect Percy of stealing the Lightning Bolt when it's obvious that Percy doesn't even suspect the existence of Zeus, let alone the god's favoured WMD, at the time of the theft?

These failures of internal logic ensure that viewers can't penetrate below the surface and be immersed in the fantasy.

The fallout of attempting to attract a particular demographic at the expense of the integrity of the story is that The Lightning Thief is too narrowly targeted on a teen audience to have wide appeal. It's too adult for kids and too alien for most adults: there's a powerful strain of Generation Y's reputed need for instant gratification in this story - Percy Jackson is not one for Hogwarts; forget years of training to develop and master his powers: one moment he has no powers, the next it is all at his command (which begs the question: what exactly is the purpose of Camp Half Blood, the training camp for demigods?). It's a strange message for struggling school kids: your problems are in fact gifts (dyslexia, ADHD...), and anyway, schooling is unnecessary...

The target audience is narrower still because The Lightning Thief is so unashamedly US-Centric, although that is in keeping with the novel. Having a US focus is fair enough for an American novel and film; the issue for non-US audiences however is that American culture appears to have colonised absolutely everything in Percy's world, even staking a claim to the mythology of Greece. The High School kids' banter and attitudes are, as they should be, all-American, but even when we slip into the mythological world, everyone from Nymphs to Satyrs, demigods to monsters, is as American as apple pie, and it's amazingly annoying! Camp Half Blood is a typical American school Summer Camp. Olympus, the home of the Greek Gods, has relocated to the mythical 600th floor of the Empire State Building. The list could go on, and on.

More than anything else about the movie, this will limit its wide appeal to US audiences, and at a guess, I'd be surprised if The Lightning Thief finds an audience in Greece at all!

Percy Jackson & The Olympians: The Lightning Thief is a great looking movie, the effects are excellent, and the supporting cast is strong with Sean Bean as Zeus, Kevin McKidd as Poseidon, Pierce Brosnan as Chiron the Centaur, Steve Coogan as Hades; the three leads, Logan Lerman as Percy Jackson, Brandon T. Jackson as Grover and Alexandra Daddario as Annabeth work well together and there is chemistry there. But the movie lacks both substance and the sort of internal logic which allows the viewer to suspend disbelief:  there's simply no depth to it that can sustain interest for any but an uncritical audience.

And the final verdict? The world of The Lightning Thief is brash, unsatisfying and unsubtle, a poor simulacra of the one inhabited by the original possessor of the lightning bolt, Harry Potter.