“Lord Foul's Bane: The Chronicles of Thomas Covenant the Unbeliever” by Donaldson R. Stephen
The first book in one of the most remarkable epic fantasies ever written, the Chronicles of Thomas Covenant, Unbeliever. He called himself Thomas Covenant the Unbeliever because he dared not believe in the strange alternate world in which he suddenly found himself. Yet he was tempted to believe, to fight for the Land, to be the reincarnation of its greatest hero…. THE CHRONICLES OF THOMAS COVENANT THE UNBELIEVER Book One: LORD FOUL’S BANE Book Two: THE ILLEARTH WAR Book Three: THE POWER THAT PRESERVES
In my teens, someone turned me on to a dark, strange set of sci-fi/fantasy books called The Chronicles of Thomas Covenant, the Unbeliever by Stephen R. Donaldson. I still think about them sometimes. They were some of my favorite books when I was a child.