If you're a little broad-minded and want a real hoot of a book about two journalists who decide to make the best porn film ever, I'd recommend "Once More, With Feeling" by Victoria Coren and Charlie Skelton. It's not really "dirty", but it (a) gives you an insight into a world that most of us will never venture near, (b) demonstrates that an amateur isn't necessarily the best person to do a professional's job and (c) is something of a window onto the very, very odd relationship between the two authors.

It should have been subtitled "Two Babes in the Blue Movie Woods"!

And it's almost a laugh a page.