"No one would have believed, in the last years of the nineteenth century, that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinised and studied, perhaps almost as narrowly as a man with a microscope might scrutinise the transient creatures that swarm and multiply in a drop of water." It has been a TV show, a video game and a comic, but The War of the Worlds is finally getting a live format.

No one would have believed, either, that the ominous opening sentence of HG Wells's 1898 novel The War of the Worlds would presage a century-long obsession with aliens, space invaders, flying saucers, ray guns and slimy creatures from Mars. Even the author, the son of a china shop owner from Bromley, Kent, couldn't have predicted that his "scientific romance" novel would grow into a many-headed hydra, spawning four film versions (two of them straight-to-video affairs), a TV series, a notorious radio broadcast, a rock musical, video games, comic books, animations and enough merchandise to fill a fleet of alien spaceships. Wells had a brilliant imagination, sure, but there were limits to even his powers of prediction.

Nevertheless, with that immortal opener and subsequent gripping story of the world's first alien invasion, Herbert George Wells kicked off the age of sci-fi, and became an iconic figure to space cadets, trekkies and stargazers - even among the literati.

Wells may have been working mainly in the much-maligned genre of what became known as science fiction (his novels The Time Machine, The Invisible Man and The Island of Dr Moreau are also classics of the genre), but he was more than merely the Michael Crichton of the Victorian age. His writing was powerful, commanding, visceral and - in a century when many authors mistook wordiness for weightiness - refreshingly concise. The new Penguin Classic version of The War of the Worlds clocks in at just 180 pages, which fly past at the brisk clip of a carriage in a hurry to get to Victoria Station.

Wells wrote The War of the Worlds at a time when England was in self-congratulatory mode, but with fear of future war - particularly with Germany - niggling in the back of its collective mind. The idea for the story came when Wells's brother Frank visited the author at his new home in Woking, Surrey, and posited the idea of a Martian invasion. Gripped by the concept, Wells cycled around the nearby neighbourhoods, mapping out locations for the story. "I completely wreck and sack Woking - killing my neighbours in painful and eccentric ways," Wells recalled.

With his story of a race of "unsympathetic" Martians laying waste to London without an iota of compassion or remorse, Wells hoped to shock and entertain his audience, and also to prick the bubble of comfort and complacency which had settled on England as the 20th century approached.

The novel was serialised in Pearson's magazine in 1897, the year of the second Victorian jubilee, and published in hardcover a year later. At the same time, newspapers in Boston and New York were publishing "bootleg" versions of the serial, transposing the action to American locations. But the story of a world made abjectly helpless in the face of an alien attack didn't chime with America's fast-growing gung-ho attitude.

One "sequel", written by an American journalist, has Thomas P Edison inventing anti-gravity and a death ray, and leading a fleet of spaceships to destroy the Martians.

When Orson Welles adapted The War of the Worlds for radio in 1938, using a US east-coast setting and presenting the action in a newsreel format, some listeners who missed the beginning of the broadcast thought America really was being invaded by Martians, and scrambled to escape the impending destruction.

Film-goers who arrived late to screenings of the 1953 movie version, however, were well aware that the action onscreen was fictional; that didn't stop them marvelling at the sight of flying machines laying waste to Los Angeles with their heat-rays, even though the eagle-eyed could spot that they were powered by strings. But the film, starring Gene Barry and Ann Robinson, did tap into prevailing Cold War fears, fed by such sci-fi B-movies as The Thing from Another World, which featured the immortal, totally paranoid, quote: "Watch the skies, everywhere, keep looking! Keep watching the skies!"

A 1988 TV series based on the book, but again set in the US, stretched to 42 episodes, which would have tested the endurance of even the most vigilant watcher. In 2005, Stephen Spielberg's blockbuster adaptation starring Tom Cruise was the director's third "close encounter" film, but his first in which the visitors' intent is purely evil. Cruise plays a blue-collar everyman from New Jersey, the kind eulogised in Bruce Springsteen songs, in a nightmarish post-9/11 vision of an America attacked by an unseen enemy from within.

Two other adaptations appeared in 2005, but were unsurprisingly overshadowed by Spielberg's monster hit. The first starred ageing 1980s bratpacker C Thomas Howell in the everyman role, while the second was a low-budget, low-quality attempt to remain faithful to the book's 19th-century setting. An online review read: "makes Ed Wood look like Orson Welles".

ONE OF THE more successful - and unlikely - adaptations was Jeff Wayne's 1978 musical version, a double album which featured guest vocalists Justin Hayward from The Moody Blues as the "sung thoughts of the journalist", David Essex as the Artilleryman, Julie Covington and Phil Lynott as Parson Nathaniel (changed from the original curate).

Richard Burton was recruited to voice the narrator, and his plummy, sombre tones proved ideal to convey the oppressive atmosphere of invasion. Since its release, the album has sold 13 million copies worldwide, and when a special edition CD was released last year, it landed back in the UK top 10. The fact that Spielberg's film version was also on release was, says Wayne, just a coincidence: SonyBMG had asked him to remaster the album for a 25th anniversary edition in 2003, but the project overran by two years.

"I think what was most surprising is that it was suddenly fighting for the top slot with Coldplay and James Blunt," says Wayne. "It was in the UK top 10 for 10 consecutive weeks, and we've now passed over 300 weeks in the album charts, overall. So it's had quite a run."

New York-born Wayne traces the beginnings of his rock musical back to when he was composing advertising jingles for a living, and producing and writing songs for a hot young heart-throb named David Essex. His father, Jerry Wayne, a singer and actor who had starred in Guys & Dolls on Broadway, had been urging his prodigiously talented son to write something bigger and more lasting than a radio commercial.

"He said, 'look, I know you're having great fun, you're producing, and you're having great success with David, but one of your aspirations as a composer and producer was to produce a large work, and don't you think you should start thinking about it?' So we started reading different books in different genres to see what popped up." What popped up was a single question, "what's the greatest science fiction story ever written?"

The answer was a best-selling album that found its way into many a dadrocker's record collection, next to Jesus Christ Superstar, Dark Side of the Moon and The Wall. But Wayne insists that The War of the Worlds is not a "rock opera" but merely a classic story set to music.

"I was certainly aware of those works, and I went to see Jesus Christ Superstar, and I had those two Pink Floyd albums, but using that term 'concept album' . . . or sometimes I've heard it referred to as a 'rock opera' - I never sat down to compose and produce either of those things. I was just trying to interpret the story of a classic science fiction story that for me had a lot of depth to it, and where it took me in compositionaland production terms, and as a continuous work, is just what came out of me."

NEARLY 30 YEARS later, the 62-year-old is going back into battle, leading the orchestra for the stage version of the musical, which is coming to Dublin's Point Theatre, having already toured the UK.

"I'd always dreamed that somehow, in some way, it would get presented in a live format somewhere along the lines of what we're now doing. But I think technology and cost prevented it, so coming back to it with the technology that's available now has given the opportunity to approach it with fresh eyes and ears."

Putting The War of the Worlds on stage brings problems that would daunt even Spielberg. How the hell do you recreate a Martian invasion in the Point? It's not like trying to put on Jack & the Beanstalk. The landscapes of Victorian London will be projected on a 100ft wide screen, and Wayne has assembled a cast of singers and musicians, to replicate the sound of the album as faithfully as possible.

Justin Hayward will reprise his role on the album, so expect Forever Autumn, the hit ballad from the album, to be a show-stopper. Also starring in the show are tenor Russell Watson and Irish singer Tara Blaise. But who will do the voice of Richard Burton? Actually, it's Richard Burton - or at least, a giant three-dimensional holographic head of Richard Burton, which will hover above centre stage and deliver the narration. Sounds scarier than the Martians.

"And perhaps our cherry on the cake, so to speak, if it works, is a Martian fighting machine. Somewhere around 25, 30 minutes into the show, descending from a hidden cavity within our lighting rig, comes a fighting machine that fires heat rays and does all the little bits and pieces that fighting machines are supposed to do. When it appears and does its thing, we think it's a very impressive device, it's a true achievement in engineering and mechanics - I just hope that it doesn't tip over!"

Jeff Wayne's musical version of The War of the Worlds is at the Point Theatre on Sun, Apr 30