A week ago, writing about 62-year old Hilary Boyd's Thursdays in the Park (Quercus), I coined the term "gran lit". Hardly original, you will say, (no dispute there), but it caught on. Subsequently, variations on "gran lit" appeared in the Times, the Telegraph and the Independent, as well as getting recognition in Australia's Herald-Sun.

The gran in question (Mrs Boyd) also popped up on both the ITV News at Ten and the Today Show, challenging the conventional wisdom: just because you're over 60, you're not interested in having a fling. I'm wondering how long it will be before gran lit joins chick lit, and the rest, as a term of art. That's to say, as a shorthand for a now-booming genre of fiction for the "grey market".

The development of the literary marketplace in the past 30-something years has been echoed by a new, and acute, sensitivity to the place of genre within the trade. In a market-savvy creative economy, you could say that genre has become everything. I have been able to identify 15 contemporary shades of "literature". No doubt, readers will think of others, but here are some obvious first nominations.

1. Lit lit

Two versions here.

a) Poetry. No higher form - a straight line from Shakespeare, Pope, Wordsworth, Hardy and Hughes.

b) Fiction. Also known as "literary fiction"; a genre whose contemporary exemplars include Julian Barnes, Philip Hensher and Zadie Smith.

2. Ghost lit

A surprising number of successful books (bestselling memoirs especially) are written by ghost writers. But there are also ghosted novels, too. By definition these wraith-like creatures have no names and are known only to their fellow spooks – and the publishers who depend on them.

3. Graphic book lit

4. Chick lit

The motherlode. There's far more of this lit than most readers realise. If, as some suggest, it began with Bridget Jones, there's now a second or even third generation.

5. Gran lit

A new entry: see my opening comments, above

6. Erotic lit

The quintessential expression of this genre is, of course, EL James's Fifty Shades of Grey, which has now begun to acquire some respectability with a nomination for a National Book award. My own guess is that it's a craze that will soon (if it doesn't already) seem embarrassing and ridiculous.

7. Booker lit

Fiction that plays well with Booker prize judges is sometimes characterised as unreadable and pretentious, with some justification. On the other hand, the Booker's track record of winners is impressive. As a prize, Booker is rivalled only by the Orange prize, now the women's prize for fiction. In a larger category – prize lit – Booker and Orange are the market leaders.

8. US lit

For me, the big names here are still Philip Roth, Paul Auster, and Don DeLillo. Of course, US fiction (and poetry) is too vast a canvas to be reduced to a single frame.

9. Commonwealth lit

The literature of the Commonwealth used to get a lot of commercial and critical attention. Changing readership patterns in the world have reduced the significance of "Commonwealth" writing, but it will probably survive, in some form, for another generation. (see also: 10 and 11)

10. Oz lit

Australian writing, a sub-genre of 9, used to be fashionable enough to deserve a category of its own. The market leader is Peter Carey, followed by Christos Tsiolkas, Kate Grenville and Thomas Keneally, among many.

11. Indian lit

This could be seen as a subset of either Booker lit or Commonwealth Lit, and is represented by Salman Rushdie, Vikram Seth, Amitav Ghosh and many others. For a while, it seemed as if the English literary tradition would be sustained exclusively by writers from the sub-continent.

12. Kids' lit

The past 20 years have seen a wonderful flowering of writing for children, from Philip Pullman and Julia Donaldson to Michael Morpurgo and JK Rowling. Later generations will work out why this should have been so.

13. Translated lit

The British reading public's appetite for foreign prose and poetry is (compared with that of our European neighbours) patchy. There was a boom in translated fiction in the 1980s (Kundera, Vargas Llosa, Márquez etc) but that has slowed in the last decade.

14. SF/fantasy

Science fiction is the cockroach in the house of books: it survives on scraps and never goes away. Occasionally, as in the work of HG Wells and JG Ballard, it becomes sublime.

15. Blog lit

A new entry to the field. Blogs that become books. The latest is schoolgirl Martha Payne's blog, which was published last week. Payne hit the headlines with her blog on school meals, won the support of Jamie Oliver and went on to raise £120, 000 for charity after her local council banned her from posting photographs and scathing critiques of her school dinners online. Her book, written with the help of her father, takes its title from her blog, NeverSeconds. A more serious example of a blog that became a book is The Rest Is Noise, by Alex Ross.

Book blogs, generally, remain virtual: as they should.