There was something a little spooky about being approached by the artist, Caitlin Smail. She wanted me to participate as the literary connection in the exhibition titled Secrets and Shadows that she is curating in the art gallery at Foyles bookshop.

I have arguments all the time about the word spooky - it seems that so many of us have such different ideas of what the word means. When I use the word spooky, I don't mean horror. I mean that which makes the hairs on the back of your neck prickle in a disturbing, yet rather pleasant way. Smail's group exhibition, which is described as having a theme of 'the darker side of the human psyche' does just this.

I guess it's no surprise that a bookshop might want a book tie-in with their exhibitions. As it happened, it was possible to arrange the date to coincide with the trade launch of my spooky novel, Thirteen. So, Thirteen artists - that is to say, twelve visual artists plus me - would come together on the 13th May 2008 to consider the idea of 'art as a psychological journey'. That's my bag, exactly - we are all on a psychological journey, after all, and it's not where we journey to, but whether we journey well or badly that makes all the difference.

And, of course, my novel is exactly that - a psychological journey, into alternate levels of reality: Conscious and unconscious. Nocturnal and diurnal. It deals with consensus reality and personal psychosis. The state of being stuck in the self, and of existing beyond the self...

Cailtin, it turned out, had read Thirteen, found it pleasingly spooky, and had produced a work inspired by it (If these walls could talk) which is featured in the exhibition. The exhibition is subtitled, The twilight world of Thirteen, and people might find it to be a psychological space that makes the hairs on their necks stand to attention.

It has to be said that I seem to have had quite a lot of spooky periods in my adult life. I suffered paranoia and general weirdness for some time after being prescribed Mefloquine, the controversial malaria medication that has been associated with uneasy psychological side effects. I then became a night taxi driver (the background for Thirteen), and learned that nocturnal and diurnal realities can be radically different from each other. Later still, I experienced three months of strangeness following a concussion that I sustained in a cycling accident on one of Brighton's eccentric cycle lanes in 2005. I lost my sense of self, the comfortable familiarity of my usual state of consciousness, for nearly twelve weeks. It seems that consciousness likes to be certain of itself - to feel rooted in identity. It's as if a statement such as "This is who I am," or "that is what I believe" keeps us sane, while, "I don't know who I am," makes us feel both more alive but also more fearful.

What makes us feel strange, mysterious and unsettled will always be, paradoxically, both attractive and yet frightening to us. It's as if we know that the deepest truth resides in the uncanny, but that to embrace the uncanny is to - inevitably - learn more about who we really are. Perhaps the most scary thing of all.

Secrets and Shadows takes place from Monday May 12 until Sunday May 18 at Foyles Gallery, Foyles Book Shop, 113-119 Charing Cross Road, London WC2.