The Way of Wyrd by Brian Bates

Sent on a mission deep into the forests of pagan Anglo Saxon England, Wat Brand, a Christian scribe, suddenly finds his vision of the world turned upside down.

The familiar English countryside is not what it seems; threatening spirits, birds of omen and plants of power lurk in this landscape of unseen terrors and mysterious forces. With Wulf, a sorceror and mystic, as his guide, Wat is instructed in the magical lore of plants, runes, fate and life force until, finally, he journeys to the spirit world on a quest to encounter the true nature of his own soul.

I loved this book, it''s like diving into the earth and swimming around in its dark comfort.