Mark Valentine is an English editor and writer of ghost or supernatural stories, and an essayist on book-collecting. 
Valentine's short stories have been published in a number of collections and in anthologies. The Collected Connoisseur (Tartarus Press, 2010) is about the adventures of an occult detective whose real name is never revealed, some written jointly with John Howard (author). ‘The Descent of the Fire’, a story in this series by Valentine & Howard, was included in the 2004 World Fantasy Award winning anthology Strange Tales edited by Rosalie Parker. Herald of the Hidden (Tartarus Press, 2013) collects stories about Ralph Tyler, a Northamptonshire psychic sleuth.
Other short story collections include Selected Stories (2012) and Seventeen Stories (2013). His story ‘Vain Shadows Flee’ was chosen for Best British Short Stories 2016 edited by Nicholas Royle (Salt Publishing). Secret Europe (2012) and Inner Europe (2018) are shared collections with John Howard of stories set in real and fictional European locations.
Studies and essays
He has written studies of Arthur Machen and Sarban. He also wrote numerous articles for Book and Magazine Collector, and his essays on book-collecting, minor writers and related subjects have been collected in Haunted By Books (2015) and A Country Still All Mystery (2017).
Valentine has edited or introduced over forty books, mostly in the supernatural fiction field, including editions of work by Walter de la Mare, Robert Louis Stevenson, Saki, J. Meade Falkner and others. He has also edited anthologies, including The Werewolf Pack (Wordsworth, 2008), The Black Veil (Wordsworth, 2008) and The Scarlet Sin – Stories for Dorian Gray (The Swan River Press, Dublin, 2017).
From 1985 to 1988, he edited Source, a journal about ancient holy wells. He then co-edited (with Roger Dobson) Aklo, a journal of the fantastic,  and currently edits Wormwood, a journal of fantastic, supernatural and decadent literature.
In small press publishing, with Roger Dobson he ran Caermaen Books, principally devoted to titles about Arthur Machen and, with Jo Valentine, he has issued handmade artist books under the Valentine & Valentine imprint. Valentine also published the first book by Joel Lane, a chapbook titled The Foggy, Foggy, Dew. 
Valentine has also issued sound recordings. As The Mystic Umbrellas, he contributed "Journey to the West", a keyboard piece, to the Deleted Funtime tape (Deleted Records, Dec 009, 1980), and as Radio Dromedary contributed treated shortwave recordings to National Grid 2 (Conventional Tapes, CON 015, 1981). He also issued The Sound of the Sea/The Sound of Pendeen Watch, a sound recording of the sea and a Cornish lighthouse foghorn (Zennor Hill tapes, 1983).
- In Violet Veils, Tartarus Press (Horam, Sussex), 1999
- Masques and Citadels, Tartarus Press (North Yorkshire), 2003
- The Rite of Trebizond and Other Tales, with John Howard, Ex Occidente Press (Bucharest, Romania), 2008
- The Nightfarers, Ex Occidente Press (Bucharest, Romania), 2009
- The Collected Connoisseur, with John Howard, Tartarus Press (North Yorkshire), 2010
- The Mascarons of the Late Empire & Other Studies, Passport Levant (Bucharest, Romania), 2010
- The Peacock Escritoire, Passport Levant (Bucharest, Romania), 2011
- Secret Europe, with John Howard, Ex Occidente Press (Bucharest, Romania), 2012
- Selected Stories, Swan River Press (Dublin), 2012
- Herald of the Hidden & Other Stories, Tartarus Press (North Yorkshire), 2013
- Seventeen Stories, Swan River Press (Dublin), 2013
- The Uncertainty of All Earthly Things, Zagava (Germany), 2018
- Inner Europe, with John Howard, Tartarus Press (North Yorkshire), 2018
- At Dusk, Ex Occidente Press (Bucharest, Romania) 2012
- Star Kites: Poems & Versions, Tartarus Press (North Yorkshire), 2013
- Arthur Machen, Seren Books, 1985
- Time, a Falconer: A Study of Sarban, Tartarus Press (North Yorkshire), 2010
- Haunted By Books, Tartarus Press (North Yorkshire), 2015
- A Country Still All Mystery, Tartarus Press (North Yorkshire), 2017
- The Garden of Ruin, God of the Rain, Fetish Press, 1980
- The Holy Wells of Northamptonshire, The Hundreds Press, 1984
- The Paravine Cries, The Stenbock Society, 1996
- The English Leopard: An Heraldic Dialogue, privately printed, 2005
- A Revelation of Cormorants, Night Jar Press, 2010
- And I'd Be the King of China, L’Homme Récent (Bucharest,Romania), 2014
- As Blank As the Days Yet To Be, Voices in a Lane, 2017
- Author entry at the Supernatural Fiction Database
- Arthur Machen, Seren Press, 1985 Archived 2011-07-16 at the Wayback Machine.
- Time, A Falconer: A Study of Sarban, Tartarus Press, 2010 Archived 2010-11-21 at the Wayback Machine.
- Nicholas Royle, "Joel Lane: The Conscience of the Circuit", in Black Static, Magazine,#38, January/February 2014m (pp. 4-9).