WHAT MAKES Guy Gavriel Kay the most interesting writer of high fantasy around today is his willingness and ability to explore new territory in, each new book. Having written one of the best post-Tolkien trilogies in the Fionavar Tapestry, he refused to repeat himself and instead created, in Tigana, a new world and a powerful tale of political revolution and personal discovery, set in a culture not unlike that of Italy in the early Renaissance, with its own forms of magic entwined in the enduring laws of the human heart. Now, having turned for inspiration to a slightly earlier period in Provence, the home of the troubadours and courtly love, he has composed the equally complex and moving A Song for Arbonne.

A Song for Arbonne is fully up to the high standards Kay has set in his previous novels: it is a complex and riveting adventure, a tale of love and passion as well as an investigation into what makes for honourable patriotism, and a loving exploration of the roots of art, here the art of the troubadours and joglars of Arbonne, a southern country in which the goddess Rian is worshipped equally with the god Corannos. To it, from its northern neighbor Gorhaut, where Corannos alone is worshipped, especially as a god of war, comes a young mercenary; his father, as high priest, seeks to invade Arbonne in order to bum its goddess-worshipping inhabitants, especially the priestesses, in a grand conflagration "honoring" his god. This man controls a new young king, and has sold out the northern reaches of his country in order to bring his terrible dream to fruition.

A true son of Gorhaut, Blaise at first cannot understand and is contemptuous of the culture of Arbonne; but although he is in some ways the major protagonist of Kay's epic, that country and its culture form the core of his book. Love, though at the heart of almost all courtly behaviour, cannot be tamed by rules, even those of a Court of Love, and the death of a duke's wife 23 years earlier, as she gave birth to another man's child, has set Arbonne's two most powerful nobles against one another in a never-ending, bitter struggle where pride and passion play equal roles. Now, as circumstances contrive to push Blaise to lay claim to the throne back in Gorhaut -naming his father and the king he anointed base traitors - the feud in Arbonne could prevent the country from joining together to withstand the coming invasion from Gorhaut. This synopsis only begins to explain the broad plot of A Song for Arbonne, but even so it fails to suggest the richness of Kay's characterizations, the subtlety of his emotional insights, the breadth of his comic and tragic social dramatizations (fully suitable to a world on a medieval/renaissance cusp, in which gods and goddesses have a real influence upon events), and the wit and substance of his writing.

Kay is one of the best stylists in high fantasy today, partly because he takes his heritage - from Homer right through to Le Guin - seriously: he makes fine use of the most ancient epic tropes, even as he introduces a complex, modem sense of love, passion, and the always difficult compromises between desire and responsibility into what has often been a psychologically superficial genre. There are a number of striking set pieces in A Song for Arbonne, but the way he has orchestrated his leitmotifs with smaller moments of individual song demonstrates his mastery most convincingly. Kay knows how to make small gestures tell as strongly as large ones, and he shifts from full orchestra to single instrument with grace and intelligence. Indeed, intelligence - about the ways in which passion intervenes in politics, about how complicated moments of action or inaction make history, about the power art can sometimes manifest in worldly activities - is what sets him apart from so many authors of redundant works in the field.

A Song for Arbonne confirms Guy Gavriel Kay's stellar reputation as a writer of serious fantasy. It is a wonderfully readable book that holds your attention throughout, as its many characters face danger and possibility, hope and desire, the potential of triumph or loss, whether of their countries or their hearts. This is fiction that asks us to believe in largesse and grandeur, in the potential integrity and grace of everyone, however difficult their realization.