Tighe lives on the wall. It towers above his village and falls away below it. It is vast and unforgiving and it is everything he knows. Life is hard on the wall, little more than a clinging on for dear life. And then one day Tighe falls off the wall. And falls, and falls, and falls ... Lavishly praised everywhere from Asimov's magazine to Interzone, ON is proof positive that Adam Roberts is a new author whose potential for greatness is rapidly being realised. ON is at once a vertiginous concept novel, a coming of age saga, a picaresque journey across a changed world and an epic adventure in the very best traditions of SF.