Lavondyss by Robert Holdstock
At the heart of the wildwood lies a place of mystery and legend, from which few return and none emerged unchanged: Lavondyss . . .
the ultimate realm, the source of all myth. When Harry Keeton disappeared into Ryhope Wood, his sister Tallis was just an infant. Now, thirteen years old, she hears him whispering to her from the Otherworld.
He is in danger. He needs her help. Using masks, magic and clues left by her grandfather, she finds a way to enter the primitive forest and begin her search.
Eventually she comes to Lavondyss itself, a realm both beautiful and deadly, a place in which she is changed forever . . .
Robert Holdstock's Mythago Wood won the World Fantasy Award and is among the most praised post-war novels of the fantastical. In this haunting sequel, Lavondyss, we are returned to the Wildwood and the mythos that Holdstock has made his own. Winner of the BSFA Award for best novel, 1989.