Stephen Donaldson, bibliography:

The Chronicles of Thomas Covenant the Unbeliever (1993)
This book at Amazon.co.uk (Europe)
Omnibus, all three volumes assembled.

The Second Chronicles of
Thomas Covenant the Unbeliever
The Wounded Land (1980)
The One Tree (1982)
White Gold Wielder (1983)

The Second Chronicles of Thomas Covenant the Unbeliever (1994)
Omnibus, all three volumes assembled.

The Gap series (science fiction)
The Gap into Conflict: The Real Story (1990)
The Gap into Vision: Forbidden Knowledge (1991)
The Gap into Power: A Dark and Hungry God Arises (1992)
The Gap into Madness: Chaos and Order (1994)
The Gap into Ruin: This Day all Gods Die (1996)

Other books:
Daughter of Regals and Other Tales (1984)
also under the name: Daughter of Regals (1984)
Epic Fantasy in the Modern World: A Few Observations (1986)

Published as Reed Stephens:
The Man who Killed his Brother (1980)
The Man who Risked his Partner (1984)
The Man who Tried to Get Away (1990) This are detective-novels.

Other peoples work about Stephen Donaldson:
Stephen R. Donaldson's Chronicles of Thomas Covenant: Variations on the Fantasy Tradition (1995)
by W.A. Senior