Apparently, although it sounds distinctly uncomfortable, everyone has a book in them.
It's probably in your appendix. There has to be some reason why they're there. Curled up inside the appendix of everyone who still has one is the germ of the novel you always intended to write. (If you've had your appendix taken out, I'm afraid your chance for creativity went with it. Sorry. You may wish to sue someone.)
Of course, the book you have in you may itself have an appendix, in which case you have an appendix in the book in your appendix, which makes everything even better, so I suggest all books should be legally obliged to include appendices from now on.
It does seem odd, though, that novels are singled out this way, as the thing everyone has one of. After all, there are a number of other ways in which people can express their creativity. Surely, if everyone has a book in them, everyone should also have a film. And a song. And a poem, and a play, and a painting, and a piece of postmodern video art, and an immersive installation theatre project about the inner life of Edwardian wombats.
The question, of course, is what you do with all that. The common cynicism is that most people should keep their novels, and other assorted creativities, inside where they belong. The recent explosion in self-publishing hasn't helped: your creative urges can now be unleashed upon an unsuspecting world for a fairly minimal amount of time and effort, and with no editing whatsoever, with the result that the market is flooded with fiction that, to put it politely, does not show its creator at their best advantage. (Obviously this isn't true of my own self-published short stories, just other people's works. Don't buy theirs. Buy mine. This has been your subliminal message for the day. Also, buy my novel, which was not self-published and is therefore irrelevant to this paragraph, but I have a PR job to do and I'm going to do it, so there. Thank you.)
But then, why shouldn't people release their novels into the wild? People get to paint pictures and put them up in their houses. They get to knit jumpers, write blogs, collect Victorian memorabilia, stuff deceased animals with slightly smaller deceased animals - self-expression comes in a million unique, endearing and sometimes disturbing forms. And people have always written, of course. The only difference is that now they can also publish.
It is a risk, though. Writers often compare writing books to having children, and there are certainly some similarities, although my children never reacted well to the editing process and personally I found toilet-training my novel a bit weird. But while your book may feel like your child to you, from the perspective of the outside world what you've basically produced is a tin. A tin of baby. You have created something that expresses and exposes yourself, that shows the world who you really are, but from everyone else's point of view it's an object. An object that nobody else, unfortunately, is obliged to like.
That's the difference between books and babies: if someone doesn't think your baby is gorgeous, they probably won't tell you so. Or if they do, they'll know that what they're doing will upset you. Whereas if someone doesn't like your novel, they may well tell you so, and if they do, you're not supposed to mind. You've got to be able to take criticism. You've got to come across as strong, confident and adult enough to deal with a difference of opinion, even though what all writers want is for everyone on the planet to praise their novel with childlike fervour and utter sincerity. And then buy a copy or several.
So yes, if everyone does have a novel in them, let it come out. But like any other object that emerges from your insides, don't assume that it will necessarily appeal to the wider world until you've polished it up a bit.
And if you really want to be associated with something that will provoke gasps of adoration and admiration, try getting a kitten instead. It's a proven fact that 99.5% of people love kittens, whereas your 200,000 word novel about a depressed 15th century Icelandic priest who learns to love himself through the medium of interpretive dance is going to appeal to a niche market at best. But then, maybe that's not why you're writing it. In summary: free kittens for all, and do what makes you happy. Especially if that's buying my book. Did I just say that out loud?