Books about Human-alien encounters -- Fiction (sorted alphabetically)
- Matter of Ethics R. R. Winterbotham
- Matter of Protocol Jack Sharkey
- Matter of Taste Jr. L. J. Stecher
- Meeting at the Summit Ivar Jorgensen
- Meeting of the Minds Robert Sheckley
- Membership Drive Murray F. Yaco
- Menace From Vega Randall Garrett and Robert Silverberg
- Menace of the Mists H. L. Gold
- Men Without a World Joseph Farrell
- Mercurian Frank Belknap Long
- Message From Mars Clifford D. Simak
- Message From Our Sponsor Henry Slesar
- Meteor-Men of Mars Harry Cord and Otis Adelbert Kline
- Mightiest Qorn Keith Laumer
- Milk Run Robert Donald Locke
- Mind Worms Moses Schere
- miniature menace Frank Belknap Long
- Miss Tweedham's Elogarsn Robert Moore Williams
- Monster of the Asteroid Ray Cummings
- Monster That Threatened the Universe R. R. Winterbotham
- Moon Maid Edgar Rice Burroughs
- Moon Maid Edgar Rice Burroughs
- Mo-Sanshon! Bryce Walton
- Mr. Meek Plays Polo Clifford D. Simak
- My Fair Planet Evelyn E. Smith