Hooper was born in Reidsville, North Carolina, United States. He earned an M.A. in education and was an instructor in English at the University of Kentucky in the early 1960s. He served briefly in 1963 as C.S. Lewis's private secretary when Lewis was in declining health. He devoted himself to Lewis's memory after his death in November 1963, eventually taking up residence in Oxford, England, where he now lives.
Hooper studied for the Anglican ministry and was ordained, serving as a chaplain and assistant priest in Oxford. He converted to the Roman Catholic faith in 1988. He is a frequent speaker at conferences and symposia.
Hooper's work has been that of a literary executor and advocate rather than independent scholar. His works include:
- C.S. Lewis: A Biography (co-authored with Roger Lancelyn Green) (1974)
- Study guide to The Screwtape Letters with Owen Barfield (1976)
- Past Watchful Dragons: The Narnian Chronicles of C.S. Lewis (1979)
- With Anthony Marchington Through Joy and Beyond: The Life of C.S. Lewis (1979)
- The Chronicles of Narnia Soundbook (TLWW, TVOTDT, PC, TSC) (abridged) with program booklet by Walter Hooper (1980)
- Through Joy and Beyond: A Pictorial Biography of C.S. Lewis (1982)
- C.S. Lewis: A Companion and Guide (1996)
- C.S. Lewis: A Complete Guide to His Life and Works (1998)
In addition, Hooper has edited or written introductions for approximately 30 books of Lewisian manuscripts and scholarship. Several of these books contain previously unknown or little-known works by Lewis.
The following works are edited by Hooper:
- All My Road Before Me: The Diary of C.S. Lewis, 1922–27. San Diego: Harcourt, 1991.
- Boxen: The Imaginary World of the Young C.S. Lewis. New York: Harcourt, 1985.
- Christian Reflections. Grand Rapids: Eerdmans, 1967.
- C.S. Lewis: Collected Letters, Volume 1: Family Letters (1905–1931). London: HarperCollins, 2000.
- C.S. Lewis: Collected Letters, Volume 2: Books, Broadcasts and War (1931–1949). London: HarperCollins, 2004.
- C.S. Lewis: Collected Letters, Volume 3: Narnia, Cambridge and Joy (1950–1963). London: HarperCollins, 2006.
- C.S. Lewis: Readings for Meditation and Reflection. San Francisco: Harper, 1992.
- God in the Dock: Essays on Theology and Ethics. Grand Rapids: Eerdmans, 1970.
- Image and Imagination. Cambridge: Cambridge University Press, 2013.
- Narrative Poems. Edited with preface by Walter Hooper. New York: Harcourt Brace Jovanovich, 1969.
- Of Other Worlds: Essays and Stories. Edited with preface by Walter Hooper. New York: Harcourt, Brace & World, 1966.
- Of This & Other Worlds. Edited with preface by Walter Hooper. London: Collins, 1982.
- On Stories, and Other Essays on Literature. Edited with preface by Walter Hooper. New York: Harcourt Brace Jovanovich, 1982.
- Poems. New York: Harcourt Brace Jovanovich, 1964.
- Present Concerns. San Diego: Harcourt Brace Jovanovich, 1986.
- Selected Literary Essays. London: Cambridge University Press, 1969.
- Spirits in Bondage: A Cycle of Lyrics. Edited with a preface by Walter Hooper. New York: Harcourt Brace Jovanovich, 1984.
- Studies in Medieval and Renaissance Literature. Collected by Walter Hooper. New York: Harcourt, Brace & World, 1966.
- The Business of Heaven: Daily Readings from C.S. Lewis. San Diego: Harcourt, 1984.
- The Collected Poems of C.S. Lewis. London: Fount, 1994.
- The Dark Tower & Other Stories. New York: Harcourt Brace Jovanovich, 1977.
- The Weight of Glory and Other Addresses (revised and expanded). Edited with introduction by Walter Hooper. New York: Macmillan, 1980.
- They Stand Together: The Letters of C.S. Lewis to Arthur Greeves (1914–1963). New York: Macmillan, 1979.
- Letters of C.S. Lewis. Edited with a memoir by W.H. Lewis. Revised and enlarged by Walter Hooper. New York: Harcourt Brace, 1988.
In 1972 Hooper was awarded the second annual Mythopoeic Scholarship Award in Inklings Studies, for scholarly contribution to the criticism and appreciation of the epic fantasy literature generated by the Inklings School, by the Mythopoeic Society.
In 1977, Hooper published the unfinished science fiction novel The Dark Tower, a previously unknown work by C.S. Lewis. The novel resembles Lewis's known works in some ways and departs from them in others. A school of critics headed by Kathryn Lindskoog accused Hooper of either forging the work in toto or adding a lot of padding onto small fragments of an unknown work by Lewis to create the published work. Lindskoog also questioned the authenticity of other posthumously published works edited by Hooper.
Hooper has rejected these accusations, and independent research exists to disprove them and confirm the authenticity of the posthumous Lewis works edited by Hooper. Professor Alastair Fowler of University of Edinburgh had Lewis as his doctoral supervisor in 1952, and he recalls discussing The Dark Tower with his mentor. This is a firsthand account of the manuscript's existence during Lewis' lifetime. Lewis' stepson Douglas Gresham also disagrees with Lindskoog's forgery claims. "The whole controversy thing was engineered for very personal reasons…. Her fanciful theories have been pretty thoroughly discredited."
- Diana Pavlac Glyer The Company They Keep: C. S. Lewis and J. R. R. Tolkien as Writers in Community. Kent State University Press. Kent Ohio. 2007. ISBN 978-0-87338-890-0
- "Mythopoeic Awards: Inklings Studies". Mythopoeic Society. Retrieved 2012-04-23.
- Kathryn Lindskoog, The C.S. Lewis Hoax (Multnomah, 1988)
- Scott McLemee, "Holy War in the Shadowlands", Chronicle of Higher Education, July 20, 2001
- Alistair Fowler, "C.S. Lewis: Supervisor", Yale Review, LXXXXI (4 October 2003), pp. 64–80.
- Harry Lee Poe, "Shedding Light on the Dark Tower," Christianity Today, February 2, 2007
- "Narnia Fans". Narnia Fans.
- "Walter Hooper Papers, circa 1940-1980", finding aid at the University of North Carolina
- "Walter Hooper", citation at the Wade Center, Wheaton College (Clyde S. Kilby Lifetime Achievement Award, 2009)
- Walter Hooper at the Internet Speculative Fiction Database
- Walter Hooper at Library of Congress Authorities, with 37 catalogue records