Loki, as a character, seems to suit our modern times exceptionally well. Of all the gods of Asgard, he is the subversive; the social and racial outsider; a gender-fluid character in a very binary world.

As a child I was a mythology purist.

I started with retellings by H. A. Guerber and Robert Graves. I read Snorri Sturluson and Saxo Grammaticus; I snapped up every translation of the Eddas and longed to read them in the original. Finally, I taught myself Old Icelandic and did just that. My interest in Norse myth dates back over forty years, and my passion for these stories has followed me throughout my life.

In the light of all this, it may seem strange that I chose to write The Gospel of Loki in the style in which I did. It's a style as far removed from the epic tone of the Eddas as you could imagine; it's filled with verbal and historical anachronisms; it's conversational, rather than heroic. This is partly due to the fact that Loki, as a character, seems to suit our modern times exceptionally well. Of all the gods of Asgard, he is the subversive; the social and racial outsider; a gender-fluid character in a very binary world. It seems appropriate, therefore, for my version of Loki to subvert the epic tradition of prose just as he subverts everything else. It is a gesture of defiance – one of many – against authority; convention; even the rules of storytelling themselves.

The Loki of the Eddas is a mercurial character. Little is known of his origins, or of Odin's reasons for befriending him. He is described as handsome, clever, silver-tongued and unreliable – in fact, "womanish" (a damning term), and he is generally unpopular in Asgard, and treated with suspicion – except, of course, when the gods are in need of his particular talents.

In the early myths he appears as a classic Trickster figure, acting more out of mischief than real malice, but by the end he becomes a sinister presence; vengeful, malevolent and self-destructive. Why does this change occur? No-one knows. The myths (and subsequent interpretations) suggest that it's simply Loki's nature to be evil. But stories and storytellers have evolved since the twelfth century. We are now less interested in the simple divisions of good-versus-evil. We have begun to enjoy a certain moral ambivalence in our heroes. And Loki is, in many ways, a typically modern antihero. In The Gospel of Loki, I've tried to provide an explanation for Loki's spiral of self-destruction, beginning with his adoption into the Asgard community, and focusing on his sense of alienation and resentment of authority. It's a very modern sentiment, and one that I think many readers will be able to identify with. The Loki of the original myths is also very funny; playing the gods against each other; playing irreverent practical jokes; defeating the enemy with nothing but his quick wits and sharp tongue. Language is his best friend and his keenest weapon – again, a very modern idea – and that's why I've chosen to write my version of Loki's story in the language of here and now; to challenge the "epic" stereotypes created by artists and scholars.

The title of "Gospel" is deliberately ironic – Loki, the liar, tells you himself not to expect the truth from him. His story is designed from the start to ridicule the tropes of epic writing. His voice is rarely heard in the myths, except in Lokasenna; the "flyting" in which Loki gleefully, cruelly and hilariously insults the gods, one by one, and exposes their failings. This is the source of "my" Loki's voice; crude, irreverent, juvenile. There's no heroic language here, just the voice of everyday folk. And that's, I think as it should be. Loki is a survivor, who has managed to adapt perfectly to the changing times, and who still seems very much at home in the twenty-first century. It seems appropriate, therefore, for him to speak with the voice of disaffected youth; of revolt; of protest. The rest of the gods seem like a stuffy, outmoded lot in comparison, high in their citadel in the sky. But Loki is the spirit of change, of chaos and of anarchy – and thus, will live forever.

Read an excerpt from The Gospel of Loki