Hundreds of people gathered at London's South Bank today dressed in differing hues of dressing gown and carrying towels to mark the resurrection of a fondly remembered sci-fi classic.

They were celebrating the 30th anniversary of the first book in Douglas Adams's Hitchhiker's Guide to the Galaxy comic series and the publication today of And Another Thing …, written by Eoin Colfer, the novelist chosen by Adams's estate to ensure the return of bemused Earthling hero Arthur Dent and others thought to have been wiped out in the fifth book of the series written by Adams before he died from a heart attack in 2001.

By agreeing to the task, Colfer, whose own Artemis Fowl series has already outsold the Adams favourites, 18m copies to 16m, is helping to cement a publishing trend set by Sebastian Faulks's officially approved 2008 James Bond revival, Devil May Care.

Dent's dressing-gown garb, and towels as carried by Ford Prefect, the alien who first saves him when Earth is about to be obliterated to make way for a hyperspace highway, have become totemic symbols of a multimedia brand that began life as a radio series in 1978 and spawned TV, cinematic, comic and computer adaptations.

Others on display at a fans' convention at the Royal Festival Hall included a spacesuit worn by a Vogon, the bureaucratic species with the most aggression and worst poetry in the universe, and glasses in which to serve pan galactic gargle blasters, along with Adams's bath, in which the author claimed to have had some of his best ideas.

The new book begins with an old favourite, two-headed Zaphod Beeblebrox, trying to save Dent and Prefect from oblivion in a London club but all seems doomed until a previously minor character from the Hitchhiker canon, the Infinitely Prolonged Wowbagger, a grumpy immortal alien out to insult everyone in the universe, comes to their aid.

Colfer, who described his previous work as "traditional fantasy adventure with a touch of James Bond and a lot of Inspector Clouseau", said his new offering was a labour of love. Initially he had been doubtful about the project, but those who approached him "said it would be a nice way to bring a new generation of people to the original books". What would Adams think of the new book? "I would hope he had a little giggle and would enjoy the respectful but not slavish way I have entered his universe … I don't think he would be disgusted."

Adams's agent, Ed Victor, said his widow Jane and daughter Polly had "loved every word" of the Artemis Fowl books, adding: "He has kind of channelled Douglas in a way. I feel 100% sure Douglas would have loved this book."

Meanwhile, at the convention, fans spoke of their love of Adams's work. "I always wanted to be Ford Prefect when I grew up," said Victoria Peterson, 35, a computer programmer from Cambridge who looked nothing like screen portrayals of the guide's researcher from a small planet somewhere in the vicinity of Betelgeuse.

"I read the books when I was about 14 and carted them around like they were relics." And, she pointed out, the eccentric electronic guide that gave the series its name bore more than a passing resemblance to her iPhone.

Phillipe Bosher, 16, from Egham, Surrey, said: "A couple of years ago my grandad got me into it. I couldn't stop reading it and then he bought me the radio programmes. It is funny, it is clever, It really gets the grey matter going." He was already a fan of Colfer's books, and had so far read half of And Another Thing... "He has managed to capture the sense of the radio series which , in my mind, is the best version. "

John Coxon, a student and secretary of fan group ZZ9 Plural Z Alpha, said he had read previews of Colfer's addition and thought it was "certainly as good as the later books Adams wrote", while Niall "Bresy" Breslin, leader and songwriter of Irish band The Blizzards, whose new CD single celebrates the new novel, remembered how "our English teacher used to read Hitchhikers to us when we were 12 or 13. I don't think any us got it but … it was the fact it was not something like a Charles Dickens novel, it was cool. I read it again when I was 18 or 19 and loved it." The tribute single was "a three-minute pop track" rather than "something Pink Floydy" or about spaceships.