Guardians of the Forest (Warhammer Novels) by Graham McNeill

The Dark Forest of Athel Loren, home of the Wood Elves, is a place of mystery and danger, a place no mortal man dares enter. Leofric, a noble knight of Bretonnia, has been raised since birth to shun and fear the forest and its enigmatic denizens. But a beastman plot to corrupt the sacred places of Athel Loren throws Leofric into an uneasy alliance with the wood elf Kyarno as they battle the invasion. If the Beastmen succeed, not only will the elves and their forest home be wiped off the face of the earth, but the destructive spirits of the forest will be unleashed to lay waste to all Bretonnia.