The Mammoth Book series

• The Mammoth Book of Short Horror Novels (1988)
• The Mammoth Book of Historical Whodunnits (1993)
• The Mammoth Book of Historical Detectives (1995)
• The Mammoth Book of Fairy Tales (1997)
• The Mammoth Book of New Sherlock Holmes Adventures (1997)
• The Mammoth Book of Comic Fantasy (1998)
• The Mammoth Book of Arthurian Legends (1998)
• The Mammoth Book of British Kings and Queens (1998) This was the US title for British Monarchs
• The Mammoth Book of Men o' War (1999)
• The Mammoth Book of Seriously Comic Fantasy (1999). Published in the US as The Mammoth Book of Comic Fantasy II
• The Mammoth Book of Sword and Honor (2000)
• The Mammoth Book of Locked Room Mysteries and Impossible Crimes (2000)
• The Mammoth Book of Awesome Comic Fantasy (2001)
• The Mammoth Book of Hearts of Oak (2001). Published in the US as The Mammoth Book of Sea Battles (2001)
• The Mammoth Book of Historical Whodunnits (Volume 2) (2001). Published in the US as The Mammoth Book of More Historical Whodunnits
• The Mammoth Book of Fantasy (2001)
• The Mammoth Book of Science Fiction (2002)
• The Mammoth Encyclopedia of Modern Crime Fiction (2002)
• The Mammoth Book of Egyptian Whodunnits (2002)
• The Mammoth Book of Roman Whodunnits (2003)
• The Mammoth Book of Roaring Twenties Whodunnits (2004)
• The Mammoth Book of Sorcerer's Tales (2004)
• The Mammoth Book of Comic Fantasy (2005)
• The Mammoth Book of New Jules Verne Adventures (2005) (with Eric Brown)
• The Mammoth Book of King Arthur (2005)
• The Mammoth Book of Historical Whodunnits: Third New Collection (2005). Published in the US as The Mammoth Book of New Historical Whodunnits (2005)
• The Mammoth Book of Comic Fantasy: Fourth All-New Collection(2005). Published in the US as The Mammoth Book of New Comic Fantasy
• The Mammoth Book of Extreme Science Fiction (2006)
• The Mammoth Book of Jacobean Whodunnits (2006)
• The Mammoth Book of Perfect Crimes and Impossible Mysteries (2006)
• The Mammoth Book of Dickensian Whodunnits (2007)
• The Mammoth Book of Extreme Fantasy (2008)

Smarties series

• All the Incredible Facts You Ever Need to Know (1999). Later split into two books as Wacky World (2001) and 'Hairy Humans (2001)
• Incredible Monsters (2000). Later split into two books as Beautiful Beasties (2001) and Deadly Dinosaurs (2001)

Story of the Science Fiction Magazines series

• The History of the Science Fiction Magazine, Part One: 1926-1935 (1974)
• The History of the Science Fiction Magazine, Part Two: 1936-1945 (1975)
• The History of the Science Fiction Magazine, Part Three: 1946-1955 (1976)
• The History of the Science Fiction Magazine, Part Four: 1956-1965 (1978)

• The Time Machines. The Story of the Science-Fiction Pulp Magazines from the Beginning to 1950 (2000)
• Transformations. The Story of the Science Fiction Magazines from 1950 to 1970 (2005)
• Gateways to Forever. The Story of the Science-Fiction Magazines from 1970 to 1980 (2007)

Other reference books

• Who's Who in Horror and Fantasy Fiction (1977)
• Fantasy Readers' Guide No. 1: The John Spencer Fantasy Publications (1979)
• The Seven Wonders of the World (1979)
• Fantasy Readers' Guide No. 2: The File on Ramsey Campbell (1980)
• The Complete Index to Astounding/Analog (1981)
• The Writings of Barrington J. Bayley (1981)
• The Illustrated Book of Science Fiction Lists (1982)
• Monthly Terrors (1985) (with Frank H. Parnell)
• Science Fiction, Fantasy and Weird Fiction Magazines (1985) (with Marshall B. Tymn)
• Algernon Blackwood: A Bio-Bibliography (1987)*
• The Work of William F. Temple (1994)
• The Supernatural Index (1995) (with William G. Contento)
• The Life and Times of King Arthur (1996)
• British Monarchs (1998). Published in the US as The Mammoth Book of British Kings and Queens. Subsequently edited and reissued as A Brief History of British Kings and Queens (2002)
• Starlight Man: The Extraordinary Life of Algernon Blackwood (2001). Published in the US as Algernon Blackwood: An Extraordinary Life.
• The Gernsback Days: The Evolution of Modern Science Fiction from 1911-1936 (2004) (with Robert A. W. Lowndes)
• The Age of the Story Tellers: British Popular Fiction Magazines 1880-1950 (2006)
• Taking Liberties (2008)

Arthurian Anthologies

• The Pendragon Chronicles: Heroic Fantasy from the Time of King Arthur (1990)
• The Camelot Chronicles: Heroic Adventures from the Time of King Arthur (1992)
• The Merlin Chronicles (1995)
• Chronicles of the Holy Grail (1996). Also published as Quest for the Holy Grail (1997).
• The Chronicles of the Round Table (1997). Also published as Tales of the Round Table (1997).

Other anthologies or single-author collections

• Souls in Metal: an Anthology of Robot Futures (1977)
• Weird Legacies (1977)
• SF Choice '77 (1977)
• The Best of British SF in 2 volumes (1977)
• Mrs. Gaskell's Tales of Mystery and Horror (1978)
• Jewels of Wonder (1981)
• Algernon Blackwood's Tales of the Supernatural (1983)
• Crypt of Cthulhu #62 (1989). Guest edited special issue dedicated to Robert A. W. Lowndes.
• Robert E. Howard's World of Heroes (1989)
• The Magic Mirror: Lost Supernatural and Mystery Stories by Algernon Blackwood (1989)
• When Spirits Talk (1990)
• The Giant Book of Myths and Legends (1995)
• Classical Stories (1996). Revised and expanded as The Giant Book of heroic Adventure Stories (1997)
• Classical Whodunnits: Murder And Mystery from Ancient Greece And Rome (1996)
• Space Stories (1996). Published in the US as The Random House Book of Science Fiction Stories (1997)
• Fantasy Stories (1996). Published in the US as The Random House Book of Fantasy Stories (1997) *Shakespearean Whodunnits (1997)
• Shakespearean Detectives (1998)
• Royal Whodunnits: Tales of Right, Royal Murder And Mystery (1999)
• Phantom Perfumes and Other Shades: Memories of Ghost Stories Magazine (2000)
• A Haunting Beauty (2000). Collection of stories by Charles Birkin.
• The Merriest Knight: The Collected Arthurian Tales of Theodore Goodridge Roberts (2001)
• The Mirror and Other Strange Reflections (2002). Collection of stories by Arthur Porges.
• Thing of Darkness (2006). Collection of stories by G. G. Pendarves compiled with John Pelan.
• Great American Ghost Stories (2008)
• Unforgettable Ghost Stories by Women Writers (2008)
• Dreams and Wonders: Stories from the Dawn of Modern Fantasy (August 2010, ISBN 0-486-47775-4)