Fifty Shades of Grey is the first in her trilogy of novels, dubbed “mommy porn” in the US for their unique brand of sadomasochistic erotica. The series about a 21-year-old student, Anastasia Steele, who embarks on a relationship with Christian Grey, a mysterious billionaire with a penchant for bondage, has already proved a runaway success in the fiercely competitive eBook market. They have also been available in print form, via a small publishing house in Australia – but became the subject of a major bidding war earlier this year between mainstream publishers keen to cash in on their popularity. The victors, Arrow, release their hard-copy edition of the first book today, and it’s doubtless already lining the shelves of your local Waterstones.