In the beginning was the tree. The stone ball rushed through emptiness. Under the crust was fire. Rocks boiled, gases seethed. Blebs burst through the crust. Dense salt water clung to the rolling ball. Slime slid on it and in the slime shapes shifted. Any point on a ball is the centre and the tree was at the centre. It held the world together, in the air, in the earth, in the light, in the dark, in the mind. [location 120]The thin child (never named, though clearly Byatt herself) is growing up during the Second World War. Her father is absent, fighting in the war: she doesn't believe he will ever return. More than anything she fears boredom. Then she acquires a copy of Asgard and the Gods (Wilhelm Wagner's massive 1880 compendium of Norse mythology 'for boys and girls'). Through the legends therein, and the equally implausible tales she hears at Sunday School and reads in Bunyan, the thin child learns to understand the world in terms of the wolves in the mind, the ineluctable surge of story, the way the gods hold the world together against chaos. ("The words men used to describe the gods were the words they used for fetters or bonds". [location 481])
The result is an inventive retelling of Ragnarok, the Norse cosmology of the end of the world (and the gods). Like several other modern authors -- Diana Wynne Jones and Joanne Harris, to name but two -- Byatt is fascinated by, and sympathetic to, the ambiguous Loki. There's joy in her descriptions of the Wolf-father and his child, in her depiction of Loki's interest in everything, the way he's captured while distracted by the form and topography of a net, the chaos (flames, waterfalls) in which he dwells.
Byatt's perspective on the myth isn't simple revisionism, though. She braids and contrasts the grim and bloody landscape of the myths with the thin child's explorations in the idyllic English countryside. The thin child's perceptions are coloured by the war that suffuses her world; trying to balance the 'good' Germans of the stories with the enemy her father is fighting, she reenvisions German bomber squadrons as the Wild Hunt ("if any hunter dismounted, he crumbled to dust" ). Byatt invents Rándrasill, an oceanic analogue of the world-tree Yggdrasil. And she regenders Jörmungandr, the Midgard Serpent, as female; not a monster but a victim, an innocent and exuberant creature driven to madness and destruction by Thor and Odin's cruelties.
I could quote whole pages of Ragnarok for the sheer beauty of Byatt's prose; I could cherrypick phrases that resonate, observations about the nature of myth, parallels between the world of the gods and the world in which the thin child reads their stories. Ragnarok works on a number of levels: a retelling of well-known stories; a questioning of the gods' morality; an exploration of the nature of myth; a reverie on a child's experience of the Norse sagas; a cautionary tale of ecological catastrophe and the human urge to destructiveness. Byatt's afterword (some of which also appears in a 2011 article for the Guardian, here) discusses these elements, but seems superfluous after the depth and passion of the novel itself.
All there was was a flat surface of black liquid glinting in the small pale points of light that still came through the starholes. A few gold chessmen floated and bobbed on the dark ripples... The black thing in her brain and the dark water on the page were the same thing, a form of knowledge. This is how myths work. They are things, creatures, stories, inhabiting the mind. They cannot be explained and do not explain; they are neither creeds nor allegories. The black was now in the thin child’s head and was part of the way she took in every new thing she encountered. http://www.wordle.net/show/wrdl/5532956/Byatt_Ragnarok