I'm not in favour of defining books too heavily by genre, as those of you who've been following this website (and y'know, these days, who isn't?) may be aware. Leads people to miss books that they'd otherwise enjoy because of preconceptions about the genre; leads writers to get distracted and either leave out nice ideas or force in material that doesn't belong.

Having been reading A Room of One's Own by Virginia Woolf recently, I find she makes a similar point. She's talking about the problem of women writers who break off from their story to address the problem of sexism in society, thus disrupting their work - but she puts her finger on a wider problem than that, which is just as applicable to genre writing if you substitute the genre of your choice for the word 'woman' (especially if you consider that at the time, 'women's writing' was pretty thoroughly in the ghetto):

She met that criticism [of her sex] as her temperament dictated, with docility and diffidence, or with anger and emphasis. It does not matter which it was; she was thinking of something other than the thing itself. Down comes her book upon our heads. There was a flaw in the centre of it. And I thought of all the women's novels that lie scattered, like small pockmarked applies in an orchard, about the second-hand bookshops of London. It was the flaw in the centre that had rotted them. She had altered her values in deference to the opinion of others.

It's 'thinking of something other than the thing itself' that scuppers writing, whether it's self-consciously literary or resolutely genre. The best books are always focused on the thing itself, and not the genre the thing is intended to occupy. But if you think too much about what other people expect your book to be, purely because of the little note on the back cover that says 'crime' or 'historical fiction', then you're distracted. The time to worry about genre is after the book is finished. Or hey, not even then.