- The Machine (short story by John W Campbell published 1935)
- The Magic Labyrinth (novel by Philip Jose Farmer published 1977)
- The Main Experiment (novel by Christopher Hodder-Williams published 1966)
- Man From Mundania (novel by Piers Anthony published 1989)
- The Man Who Awoke (novel by Laurence Manning published 1977)
- Manalone (novel by Colin Kapp published 1977)
- The Maracot Deep (novel by Sir Arthur Conan Doyle published 1929)
- Masters Of The Vortex (novel by E E doc Smith published 1968)
- Maxwells Demon (novel by Martin Sherwood published 1976)
- The Mayors (novelette by Isaac Asimov published 1942)
- The Merchant Princes (novelette by Isaac Asimov published 1944)
- Messengers Of Darkness (novel by Hugh Walker published 1979)
- Methuselahs Children (novel by Robert A Heinlein published 1958)
- Micromégas (novel by Voltaire published 1752)
- Mirror Image (short story by Diana L Paxson published 1983)
- Mirror Image (novel by Michael G Coney published 1975)
- Mix-Up (short story by George Collyn published 1964)
- The Monadic Universe (collection by George Zebrowski published 1977)
- Monolog (short story by Philip Jose Farmer published 1973)
- Monologue (short story by Philip Jose Farmer published 1973)
- Mort (novel by Terry Pratchett published 1987)
- The Mule (novella by Isaac Asimov published 1945)
- The Mutants (novel by Kris Neville published 1966)