Bookshops gear up for the great 'Inheritance' rush

He treated himself to a collectors' piece blade made of legendary Damascus steel after finishing his latest book because "every fantasy author deserves to have a good sword". But Christopher Paolini will not need to battle for sales when the final book in his popular Inheritance cycle hits the shelves on Tuesday.

Retailers are predicting that Inheritance, which marks the conclusion of the 27-year-old American's four-title series, will be one of the year's bestsellers. Waterstone's has sold tens of thousands of copies in advance, making it the biggest pre-order of a children's title since J K Rowling's final Harry Potter book, Harry Potter and the Deathly Hallows, in 2007. Yesterday, Inheritance was sixth on Amazon's UK bestseller list after 127 days in its top 100.

Paolini said he was "really happy and amazed and honoured" that readers of all ages, who have waited three years since the last book, Brisingr, were excited. "I'm excited about the story, but that's never any guarantee other people will feel the same way," added the author, whose new sword is on a stand in his office. He hopes fans feel the series' ending is "both satisfactory and surprising".

Inheritance follows the adventures of Eragon and his dragon Saphira as they continue into enemy territory towards the evil king, Galbatorix. The first three books in the fantasy series have sold 25 million copies worldwide – a considerable feat for an author who self-published 10,000 copies of his first book, Eragon, in 2001.

Paolini, from Montana, wrote the first draft at the age of 15 and later embarked on a US tour to publicise the finished book. The American novelist Carl Hiaasen recommended it to publisher Alfred A Knopf, a US imprint of Random House, which re-released the book in 2003.Eragon was published in the UK in 2004, with a film adaptation appearing two years later.

The home-schooled writer graduated from high school at the age of 15 through distance learning, and credits his parents for providing an environment that allowed him to pursue his interests. "Nowadays, we make it so that people are unable to follow or get into their career until [their] mid-twenties, if not later, and, historically, that's not always been the case," he said. "If you were interested in something, or you had an affinity for something, you would get apprenticed when you were quite young to a master craftsman of one kind or another, and I think that's something that ought to be more common. I loved writing, I loved drawing, so I just dived into it ... and it gave me a head start because I ended up getting five, six, seven, eight years of work on my craft before a lot of people in my generation."

Paolini spent a lot of time in his local library when growing up and said it was the support of public, private and school libraries that helped launch the self-published edition of Eragon. "When the apocalypse happens, it's going to be libraries that save civilisation," he said, referring to public spending cuts to libraries in the UK. "They are the storehouses of knowledge and, as much as I love computers and ebook readers and all that, all it takes is a bad solar storm or an electromagnetic pulse, or something of that nature, to wipe out all of the digital records." He said libraries were "incredibly important", and education and libraries were "investments" in society and the future.

After 13 years writing fantasy, Paolini hopes to try other genres, probably starting with science fiction. He has also collaborated with his younger sister, Angela – the inspiration for the herbalist of the same name in the Inheritance cycle – on a project "which may see the light of day fairly soon".

But it is his fantasy that is exciting booksellers. Jon Howells, a spokesman for Waterstone's, said Paolini was interesting because while everyone – whether or not they were fans – had heard of Rowling or Stephenie Meyer, the author of the vampiric Twilight phenomenon, he was "quite under the radar for a lot of people" yetInheritance would be one of 2011's biggest books. It is Waterstone's largest pre-order of the year, a feat usually achieved by the best-selling chef Jamie Oliver, whose latest title, Jamie's Great Britain, launched in September.

Fiona Kennedy, owner of the Pitshanger Bookshop in Ealing, west London, an independent bookseller, said she had been "quite surprised" by the level of interest in Inheritance as hardback novels were not easy to sell in normal circumstances. She added that Paolini had a "very dedicated following" and the book's strict embargo made the release "more of an event".

"Books like this bring people into bookshops and I think, at a more holistic level, they bring books into the public eye because they attract media attention. They're a good thing for books in general," she said.