Fry, who has more than 750,000 followers, tweeted yesterday that "You will not read a more dazzling book this year than David Eagleman's 'Sum'. If you read it and aren't enchanted I will eat 40 hats." The collection, which considers different versions of the afterlife, from a microbe-sized God unaware of humanity's existence to an afterlife where the dead are split into all their different ages, subsequently shot to number two in Amazon's bestseller charts.

Sum: Forty Tales from the Afterlives is not the first title to benefit from a plug on Twitter: in May, Jonathan Ross sent Jon Ronson's The Men Who Stare at Goats racing up the book charts after he selected it for a Twitter book club. Publisher Canongate is now rushing through a major reprint of the Eagleman collection to meet demand. "It's lovely when things come out of the blue," said publisher Jamie Byng. "I knew Stephen was a huge fan of the book [but] the impact of his tweet is just amazing. It's the ultimate word of mouth recommendation from someone [his followers] really trust, and from a publisher's point of view it's magical."