As porn books go, EL James’ Fifty Shades of Grey is limp. It has too much soppy emotion and the porn bits are mediocre and tediously repetitive. At best it can be called a Mills & Boon pretending to be porn. Yet the trilogy which includes Fifty Shades Darker and Fifty Shades Freed is gripping.

From the moment Anastasia Steel a literature student walks into tycoon Christian Grey’s office you are hooked. When he tells her to sign a contract which will make her his ‘submissive’ sexual partner, you think this is going to be about deviant sexual behaviour and some really hot sex.