Girl Meets Boy, by Ali Smith <br/> Where Three Roads Meet, by Salley Vickers

"'Let me tell you about when I was a girl,' our grandfather says." With this flourish, Ali Smith opens her contribution to the Canongate Myth Series, a blissful recasting of Ovid's Iphis legend. In this world, gender fluidity is celebrated as the principle of life itself. Shakespeare's age knew all about this: boys will be girls and vice versa. All you have to do is imagine.

The Renaissance collected the body of classical myth and reanimated it in new and virtuoso modern forms. If Canongate's redemption of classical myth is designed as a re-Renaissance, then Smith is its Spenser and Shakespeare, offering in the tale of Iphis and Ianthe a mingling of light fantastic recreation with a deeply serious criticism of male tales.

Girl Meets Boy is a feminist and ecological reimagining of Ovid's most joyful legend. But there is a dark edge of threat, for Iphis, like many a contemporary girl-child, is threatened by infanticide. Raised as a boy, she is educated alongside the beauty, Ianthe. Love blossoms, but with the approach of the wedding, so does chagrin. "Mares do not burn with love for mares, or heifers for heifers," Ovid reminds us – erroneously, as science informs us, for same-sex union is found in all creatures. On the brink of the wedding, Isis intervenes to change Iphis into a boy, complete with laddish haircut.

Smith's modern Iphis and Ianthe are lesbian lovers, Anthea and Robin. Anthea is thrilled to see the kilted Robin up a ladder painting anti-capitalist legends on a wall. The gay lovers query Ovid's tale as they share it under the duvet: "The story of Iphis is being made up by a man," Robin explains, "but Ovid's very fluid... he knows... the imagination doesn't have a gender." You don't have to turn into a boy in order to be one.

Smith represents the ecstasy of sexual union as refusal of boundaries, in passages of ecstatic prose-poetry: "Her hand became a wing. Then everything about me became a wing, a single wing, and she was the other wing, we were a bird." Nature is a magical and saturnalian plenitude that mocks social, religious and linguistic forms. A gorgeous, funny epithalamion concludes the novella as the lovers marry by the banks of the River Ness, in contradiction of all dour Presbyterian forms: "Ness I said Ness I will Ness." Jaunty lightness, carefree, labile inventiveness and powerful tenderness work their magic on the reader.

Sally Vickers's Where Three Roads Meet is an intelligent and thoughtful trinity of narratives, situated at the junction of Greek religion and psychoanalysis. Sigmund Freud is stoically suffering through his last years, with a "monster" in his mouth owing to his hideous oral cancer, which makes more terrible his flight from the monstrous growth of Nazism in his native land. Exiled, stigmatised, dumb-struck, he is visited by a strange but courteous Greek: Tiresias, Sophocles's blind prophet, who tells him the tale of Oedipus. To Tiresias, the story is divinely inspired: at Pythia the oracle receives the sacred ecstasy of possession. To Freud, however, "what you call a god is a projection occasioned by the desire to revert to a state of infantile dependency". How desiccated and reductionist he sounds in the context of Tiresias's poetry.

Vickery's Freud sneers at Virginia Woolf, "all head and no genitals". Anna Freud punctuates the conversations, an Antigone of the tea-table. If Iphis and Ianthe represent infantile dependency, as they swim in the amniotic ocean of polymorphous bliss, bring it on. It is Vickery's Freud's tragedy to be exiled from the interior of his myths, shut out of their illusions, a grandfather who will never guess how things might have been "when I was a girl".

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Canongate £12.99 (199pp) £11.69 (free p&p) from 0870 079 8897

Stevie Davies's 'Kith & Kin' is published by Phoenix