ANYONE WITH A MIND SO full of zany, fantastic, original and funny ideas had to be just a little bit mad, I thought. Or, at the very least, exotically eccentric. It wasn’t just Jasper Fforde’s books that led me to that expectation. I had looked up his web-site. The index alone has more than 600 references; that’s before you start reading any content. Was this the sign of an egocentricity so vast as to amount to the unbalanced mind I’d been searching for?

I was ill-prepared for normality. Fforde’s conversation is not peppered with jokes and puns (he leaves that for the printed page); he lives quietly in Wales with his partner Mari; his only indulgence is a De Havilland aircraft that he flies over the Welsh countryside; he’s obviously greatly enjoying his enormous success (all the more because writing is his second career) but is not boastful about it. “People say: ‘You write wacky, way-out books so you must be wacky and way-out.’ No, because if I was wacky and way-out I wouldn’t be able to sit down at a computer and write a book a year.”

But what about his compulsive need to provide his fans with every scrap of information, however obscure, they might want to know? That’s not normal, is it? His reason is disarming.

“It’s my after-sales service, part of the contract between me and my readers.” I suggest that his only obligation is to produce a book that his readers enjoy. But that would be to treat them with contempt, he argues.

Jasper Fforde (his real name) is the only member of an academic family not to have gone to university. His father, an economics don, was once chief cashier of the Bank of England, whose signature appeared on all banknotes of the period. Fforde chose to become a focus-puller (assistant cameraman) on many British films.

He started writing in his thirties (he’s now 46) and had completed five books – and received 76 rejections in ten years – before one of them, The Eyre Affair, was published, in 2001. He had almost given up hope.

“I don’t think any agent or publisher ever read any of the books; they looked at the synopsis and said it was too bizarre. I got the feeling I wasn’t ever going to be published. But I was enjoying the writing so much, so I said what the hell, I can do whatever I want, because it didn’t matter, I wasn’t going to be published anyway. So I decided to bung it all in, add all those ideas I had, one sub-plot after another, and after doing that I felt I had a book which really worked, in a way which hadn’t been done before.” The Eyre Affair took off quickly, here and in the US.

There are now five books in his Thursday Next series. The heroine, a literary detective based in contemporary Swindon (though the Crimean War has not yet ended, and dodos are house pets), travels into the contents of famous books to save their characters and plots, and even saves great literature itself from evil enemies.

In The Eyre Affair,Next confronts an arch-villain who has been killing off minor characters in Dickens, then kidnaps Jane Eyre. In Next’s fifth and latest adventure, First Among Sequels, published in early July, she investigates the premature deaths of Sherlock Holmes and Miss Marple, Pride and Prejudice is turned into a reality show called The Bennets and she meets a fictional Thursday Next – herself from a previous Fforde book.

No such summaries, though, do justice to the sheer inventiveness, wit, complexity, erudition, unexpectedness and originality of the works, nor to their vast repertoire of intricate wordplay and puns. (Players of Monopoly may recognise Landon Parke-Laine.)

But why Swindon? “Most people use Swindon as a shorthand joke, like Basingstoke or Slough, so I thought, let’s turn it on its head and say that it’s a fantastically vibrant place where there’s nothing that can’t happen.” No one since Diana Dors has made the town so famous; his fans assemble there for Fforde walking tours and Fforde festivals. The town has repaid the favour by naming four of its streets after characters in his books.

In order fully to appreciate his humour, don’t readers need to know a great deal about the fictional characters that inhabit his books? “I did worry about that at the beginning, but now I don’t worry so much. I don’t use really obscure characters. They’re ones people have heard of even if they haven’t read the book. They may not be totally au fait with Jane Eyre, but they know who she is. A lot of people haven’t read Great Expectations, but they know about Miss Havisham and her wedding dress. It doesn’t matter if they don’t catch all the references and allusions. They’ll know enough.”

His other two books deal with the escapades of the Reading police’s Nursery Crimes division, headed by DI Jack Spratt, smarting from his failure to secure the convictions of three pigs for the murder of Mr Wolff. He and his sidekick Mary Mary investigate crimes involving nursery rhyme characters. Who was responsible for Humpty Dumpty’s fatal fall from the wall? How come the three bowls of porridge in Goldilocks and the Three Bears were of different temperatures if they came out of the same bowl? And why were Mama and Papa Bear sleeping in separate beds? He intends writing only one more nursery crime book, but still has many ideas for future Thursday Next novels. Then, perhaps, he’ll create his own characters and cease relying on those invented by others. And continue to give his readers his after-sales service. He’s not only sane, but nice as well.

First Among Sequels by Jasper Fforde

Hodder, £12.99; 416pp

Buy the book here for the offer price of £11.69 (free p&p)

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