The Illearth War (The Chronicles of Thomas Covenant the Unbeliever, Book 2)

Against his will, Thomas Covenant is drawn once again out of our reality and into the strange and magical alternative world known as the Land. But forty years have passed in the Land since Covenant's last visit - forty years in which the evil Lord Foul has grown in power and built an unstoppable army. Covenant must act fast or abandon the Land to complete destruction.