TWENTY-FIVE years after the publication of his breakthrough novel Mythago Wood, Robert Holdstock has returned to the world of Ryhope Wood to continue the story of the Huxley family.

It seems, in many ways, as though Holdstock has been waiting those 25 years for his characters to grow up; as though they are as real as he is.

Although there have been other books set in the mythical lands found in the centre of Ryhope Wood, Avilion is the actual sequel to the story that began in Mythago Wood.

Since so much of Avilion is based on the concepts and ideas that Holdstock developed in Mythago Wood, the first book is almost necessary to understand the reasoning and choices of the characters in Avilion.

Set in Herefordshire in England, Mythago Wood is based somewhat on the historical and mythical stories of the ancient Britons with dashes of Norse sagas and Greek legends mixed in. In genre it is a type of fantasy literature known as mythic fiction.

Mythago Wood won the World Fantasy Award for best novel in 1985, being acclaimed for the psychological and philosophical tangents that Holdstock used to explain the experiences of his characters.

After the traumatic end to the story – with brothers pitted against each other for the love of a mysterious and beautiful woman – Avilion opens much more gently.

The old wounds, both emotional and physical, that Steven Huxley suffered at the hands of his brother Christian have been mostly healed by the birth of his children – Jack and Yssobel – and his marriage to his beloved Guiwenneth.

Half human – red – and half mythago – green, the children are now young adults and as time passes their differences are becoming more marked.

Jack longs for the world of their father, Steven, he wants to visit the family home outside the wood, he wants to see the village that Steven has described to him; he wants to explore.

Yssobel seems more 'green' than Jack. Although she seems happy enough living in the valley at the centre of the mythical wood that created her mother, Guiwenneth of the Green, Yssobel is also searching for something more.

Unlike Jack, however, Steven's daughter is somehow caught up in the mystical and mythical history of her mother, a legendary Celtic princess, and a mysterious man whom only she seems to see. She too wants to leave the valley but not to head out into the world – Yssobel wants only to head deeper into the wood and the mysteries of the mythago.

As the children grow older, their mother seems to become less and less 'real', or more a part of her mythical world, isolating herself from Steven and spending days staring into the distance.

Guiwenneth's growing distraction angers Yssobel, who after fighting with her mother suddenly disappears. Concerned, Jack decides that the only person who can explain both his mother's fading from the world and Yssobel's whereabouts, is his grandfather.

But of course, there's a problem. George Huxley is actually dead; or dispersed into Ryhope Wood, which is one and the same. Grabbing onto the opportunity, Jack heads to Oak Lodge, his father's home, hoping to raise George's spirit and find the answers to his questions.

So starts an adventure that is part action story, part romance and part coming-of-age monologue. Avilion is an example of fantasy literature that uses imagined worlds to look more closely at our own.

The 'mythagos' of Holdstock's books are like literary versions of Freud's id, the uncoordinated instinctual trends of our minds, while their human counterparts perform the function of the ego - the organised realistic part of the psyche.

In the characters of Jack and Yssobel, Holdstock is attempting to show how a fully integrated person needs to be made up of both the id and the ego – the instinctual and the realistic – in order to function.

The question at the core of Avilion is whether or not this is possible. Are we all, like Jack and Yssobel, either too much id or too much ego? Are we unbalanced in our internal psyches?

Will Jack be able to integrate his love of his father's world – Oak Lodge and the village of Shadoxhurst – with his 'green' abilities? Will Yssobel's journey to discover the truth of her mother through time and history stop her from remaining a flesh and blood creature?

Avilion, like Mythago Wood before it, is not an 'easy' read. There are philosophical ideas, historical figures and a great deal of emotional angst in Holdstock's work. It is, however, a piece of fiction that is worth the label of literature.

While I personally have a few problems with some of Holdstock's symbolism and his simplistic choices, they don't need to take too much from your enjoyment of the novel.

Holdstock's decision to make the female characters all about emotion and instinct, beings that are wild and fickle like nature; while the men are all rational, logical, practical and violent; is a bit patronising in this day and age.

Still, Avilion is a worthy successor to Mythago Wood, and well worth the 25-year wait.

Avilion by Robert Holdstock is published by Gollancz and is available from good book stores and online.