From The Naked Civil Servant, by Quentin Crisp:
Now that the marketing of all goods, including books, has become a shameless hoax practised on innocent consumers, the works of M Zola are packaged to look as if they were by Mr Spillane. This ruse works because no one would dare to take a book back to a shop because it wasn't as filthy as the cover promised.
That was 40 years ago. Of course, now we can get any permutation of perversity we desire just by switching off SafeSearch, nobody looks to the literary classics for smut, at least not directly. They get the smut from the TV adaptations, or at least from Andrew Davies's heavy pre-transmission hints about the amount of filth he's packed in this time, although they never turn out to be as naughty as he suggests. Meanwhile, publishers have to sell Austen and Dickens and Gaskell on the basis of them being on the telly, with that one you like in it, you know, that one with the nice hair.
But Crisp's essential point still holds, I suppose. Nobody's ever taken a book back because it didn't have a damp Colin Firth in it.