As many fans are aware, the "official" Conan paperbacks (published by Lancer Books in the 1960s and later published by Ace Books) were edited by L. Sprague de Camp.  A few stories were extensively rewritten by Mr. de Camp: "The Frost-Giant's Daughter," "The Black Stranger" (retitled "The Treasure of Tranicos"), and "The God in the Bowl," in particular, were heavily revised.  Mr. de Camp rewrote four unpublished non-Conan stories to turn them into Conan tales: "The Bloodstained God," "Hawks Over Shem," "The Road of the Eagles," and "The Flame Knife" were NOT Conan tales as REH wrote them.  De Camp, along with Lin Carter, "completed" several unfinished Conan stories (fragments, synopses, etc.) left by REH, and they and Bjorn Nyberg also contributed several out-and-out imitation Conan stories to the series.

For those who want to read the Conan stories as they were originally published, and who want to know the character as his creator meant him to be (or at the very least to see the character as Howard’s readers originally saw him), here is a listing of Robert E. Howard's Conan stories and fragments, and where to find them. 

The stories are listed in order of first publication of the REH version.  I prefer using Howard's original titles; the title under which the story was published, if different, is in parentheses.

"The Phoenix on the Sword"

• Weird Tales, December 1932
• Skull-Face and Others (Arkham House, 1946)
• Skull-Face Omnibus (Neville-Spearman [Jersey] Ltd., 1974; reprinted as 3-volume paperback, Panther Books Ltd., 1976)
• The Conan Chronicles Volume 2: The Hour Of The Dragon (Millenium, February 2001)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The Scarlet Citadel"

• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002) *
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The Tower of the Elephant"

• Weird Tales, March 1933
• Skull-Face and Others (Arkham House, 1946)
• Skull-Face Omnibus (Neville-Spearman [Jersey] Ltd., 1974; reprinted as 3-volume paperback, Panther Books Ltd., 1976)
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"Black Colossus"

• Weird Tales, June 1933
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"Xuthal of the Dusk" (as "The Slithering Shadow")

• Weird Tales, September 1933
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The Pool of the Black One"

• Weird Tales, October 1933
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"Rogues in the House"

• Weird Tales, January 1934
• Terror By Night, Selwyn & Blount Ltd., 1934
• Skull-Face and Others (Arkham House, 1946)
• Skull-Face Omnibus (Neville-Spearman [Jersey] Ltd., 1974; reprinted as 3-volume paperback, Panther Books Ltd., 1976)
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"Iron Shadows in the Moon" (as "Shadows in the Moonlight")

• Weird Tales, April 1934
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"Queen of the Black Coast"

• Weird Tales, May 1934
• Avon Fantasy Reader #8, 1948
• Fantastic Magazine Sword & Sorcery Annual, 1975
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The Devil in Iron"

• Weird Tales, August 1934
• The People of the Black Circle, G.P. Putnam's Sons, 1977 (also published in paperback, Berkley Books, 1977)
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The People of the Black Circle"

• Weird Tales, September 1934 (part one), October 1934 (part two), November 1934 (part three)
• The People of the Black Circle, G.P. Putnam's Sons, 1977 (also published in paperback, Berkley Books, 1977)      
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)

"A Witch Shall Be Born"

• Weird Tales, December 1934
• Avon Fantasy Reader #10, 1949
• The People of the Black Circle, G.P. Putnam's Sons, 1977 (also published in paperback, Berkley Books, 1977)
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)

"Teeth of Gwahlur" (as "Jewels of Gwahlur")

• Weird Tales, March 1935
• The People of the Black Circle (G.P. Putnam's Sons, Berkley Books)

"Beyond the Black River"

• Weird Tales, May 1935 (part one), June 1935 (part two)
• Red Nails, G.P. Putnam's Sons, 1977 (also published in paperback, Berkley Books, 1977)
• The Conan Chronicles Volume 2: The Hour Of The Dragon (Millenium, February 2001)

"The Man-Eaters of Zamboula" (as "Shadows in Zamboula")

• Weird Tales, November 1935
• Skull-Face and Others (Arkham House, 1946)
• Skull-Face Omnibus (Neville-Spearman [Jersey] Ltd., 1974; reprinted as 3-volume paperback, Panther Books Ltd., 1976)
• Red Nails, G.P. Putnam's Sons, 1977 (also published in paperback, Berkley Books, 1977)
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)

The Hour of the Dragon

• Weird Tales, December 1935 (part one), January 1936 (part two), February 1936 (part three), March 1936 (part four), April 1936 (part five)
• The Hour of the Dragon, G. P. Putnam's Sons, 1977 (also published in paperback, Berkley Books, 1977)
• The Conan Chronicles Volume 2: The Hour Of The Dragon (Millenium, February 2001)

"Red Nails"

• Weird Tales, July 1936 (part one), August 1936 (part two), September 1936 (part three)
• Red Nails, G.P. Putnam's Sons, 1977 (also published in paperback, Berkley Books, 1977)
• The Conan Chronicles Volume 2: The Hour Of The Dragon (Millenium, February 2001)

"The Hyborian Age"

• The Hyborian Age, LANY Cooperative Publications, 1938
• Skull-Face and Others (Arkham House, 1946)
• Skull-Face Omnibus (Neville-Spearman [Jersey] Ltd., 1974; reprinted as 3-volume paperback, Panther Books Ltd., 1976)
• Red Nails, G.P. Putnam's Sons, 1977 (also published in paperback, Berkley Books, 1977)
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The Vale of Lost Women"

• The Magazine of Horror, no. 15, Spring 1967
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The God in the Bowl"

• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The Frost-Giant's Daughter"

• Echoes of Valor Volume 2, TOR Books, 1989
• The Dark Man #1, Necronomicon Press, 1990 (rough draft only)
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"The Black Stranger"

• Echoes of Valor, TOR Books, 1987
• The Conan Chronicles Volume 2: The Hour Of The Dragon (Millenium, February 2001)

Untitled synopsis (as "The Hall of the Dead")

• The Last Celt: A Bio-Bibliography of Robert E. Howard, Donald M. Grant, 1976
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

Untitled fragment (as "The Hand of Nergal")

• The Last Celt: A Bio-Bibliography of Robert E. Howard, Donald M. Grant, 1976
• The Conan Chronicles Volume 1: The People Of The Black Circle (Millenium, August 2000)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

Untitled synopsis (as "The Snout in the Dark")

• Cromlech #3 (Cryptic Publications, 1988)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

Untitled fragment (as "The Snout in the Dark")

• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

Untitled synopsis (as "Drums of Tombalku")

• Cromlech #3 (Cryptic Publications, 1988)

Untitled fragment (as "Drums of Tombalku")

• unpublished in acceptable form

"Wolves Beyond the Border" (synopsis)

• unpublished

"Wolves Beyond the Border" (fragment)

• The Conan Chronicles Volume 2: The Hour Of The Dragon (Millenium, February 2001) *

“Notes on Various Peoples of the Hyborian Age” (notes)

• Gazeteer of the Hyborian World of Conan, Starmont House, 1977 (also reprinted by Borgo Press, 1991)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

“List of Hyborian Names and Countries” (notes)

• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

"Cimmeria" (poem)

• The Howard Collector, Winter 1965
• Dark Valley Destiny (BlueJay Books, 1983)
• The Conan Chronicles Volume 2: The Hour Of The Dragon (Millenium, February 2001)
• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

Robert E. Howard's Hand Drawn Maps of the Hyborian Age World

• Robert E. Howard’s Conan of Cimmeria Volume One (Wandering Star, 2002)
• The Coming of Conan the Cimmerian (Ballantine Books, December 2003)

* The last two paragraphs of “Wolves Beyond the Border” in Millenium’s The Conan Chronicles Volume 2 are taken from the last two paragraphs of Howard’s unpublished synopsis for the story.

NOTES:
     The three Berkley/Putnam volumes (Red Nails, The People of the Black Circle, The Hour of the Dragon) were also published in a 3 volume hardback set by the Science Fiction Book Club.  The type for those book club editions was reset extremely badly, rendering those reprints unacceptable. The Science Fiction Book Club edition can be identified by the lack of an ISBN number on one of the inside front/cover pages. Also, the book club editions are far thinner than the "acceptable" hardbacks. The Berkley paperbacks of the Conan stories are the most preferable, not for the Howard text, but because the “Forewords” and “Afterwords” in the Putnam and Science Fiction Book Club hardback editions were altered from their original appearances in the Berkley paperbacks.
      Donald M. Grant’s Red Shadows and The People of the Black Circle were found to be expurgated, and called into question the textual purity and integrity of the entire D.M. Grant collection of Conan books. Therefore, they have been removed from this listing.
      The first printings of Millenium’s The Conan Chronicles Vol. 1 & 2 had a tremendous amount of typographical errors. The publisher reports that the errors were corrected in subsequent printings, although to the best of my knowledge the claim has not yet been independently verified.
       The book of Robert E. Howard's Conan of Cimmeria, Volume One published by Wandering Star (as well as the paperback version The Coming of Conan the Cimmerian published by Ballantine) has a unique difference that is worth mentioning concerning the story "The Scarlet Citadel." [correction:] The editors of this book used the final version of this story taken from an original manuscript prepared by Howard six months after the story's first appearance in Weird Tales magazine. In May/June 1933, REH retyped (and somewhat revised) this story for submission to British publisher Denis Archer. A gem for Howard purists, this is the first time "The Scarlet Citadel" has been published from Howard's definitive version of the story.