Books about Human-alien encounters -- Fiction (sorted alphabetically)
- Snowbank Orbit Fritz Leiber
- Space brat Henry Slesar
- Space-Can Murray Leinster
- Spacemen lost George O. Smith
- Spawning Ground Lester Del Rey
- Special Delivery Kris Neville
- Specimen Charles V. De Vet
- Spoilers of the Spaceways W. Bradford Martin
- Stamped Caution Raymond Z. Gallun
- Star Beast Damon Knight
- Star-Crossed Lover William W. Stuart
- Star of Panadur Henry Hasse and Albert dePina
- Steel Giants of Chaos James R. Adams
- Stellar Vengeance Frank Freeman
- Strange Exodus Robert Abernathy
- Stranger Gordon R. Dickson
- stroller Margaret St. Clair
- Student Body F. L. Wallace
- Summer Guests James H. Schmitz
- Sunfire! Edmond Hamilton
- Survival Type Jesse F. Bone
- Sweeper of Loray Robert Sheckley
- Sweet Tooth Robert F. Young
- Sword Frank Quattrocchi
- Sword of Johnny Damokles Hugh Frazier Parker