Robert Langdon is back in Dan Brown’s latest thriller Inferno

Harvard symbologist Robert Langdon is back. Dan Brown's latest thriller, the Dante-inspired Inferno, puts Langdon in a hospital bed with no memory of how he wound up there. It went on worldwide sale today.

The clever professor is the only one who can figure out the doomsday puzzle, the first macabre piece of which is sewn into his bloody tweed jacket. Langdon’s appearance in The Da Vinci Code was a literary phenomenon, selling 81 million copies in 51 languages.

In a similar vein Booksellers are predicting Inferno will become the biggest-selling book of the year.

Sales of the book have already reached the highest level of customer pre-orders at retailer Waterstones since the release of Harry Potter author JK Rowling's adult fiction The Casual Vacancy last year.

"We think it's going to be the fastest and biggest-selling book of the year because Dan Brown is in a league of his own" said a Waterstones spokesman.

“The early word is that it’s darker, which will whet the appetite for everyone because this is the fourth appearance of Robert Langdon and I think giving it that sort of twist, freshens it up for long-term readers,” the spokesman added.

Brown, who is famous for his love of puzzling codes, conspiracies and other symbols, said the subject matter for the book was so vibrant and horrifying that it helped do a lot of the work for him.

“I’m not writing about the masons and ancient histories, which is kind of ethereal. I’m writing about Dante’s vision of hell,” he told The Sunday Times.

“It wasn’t until the 1300s and this version of Inferno that it became terrifying. Dante has had enormous influence on the Christian view of hell.”

The author, who said he tries not to read reviews of his books, also spoke of his unique way of dealing with writer’s block, by suspending himself upside down to help get his creative juices flowing.

“It does help. You‘ve just got to relax and let go. The more you do it the more you let go. And then soon it’s just, wow,“ he said.

The Da Vinci Code was published in 2003 and was made into a hit film starring Tom Hanks. It spent more than a year atop the New York Times bestseller list.

- Bloomberg/Reuters