Here are some gems I’ve found at used bookstores –

A Late Phoenix  Aird, Catherine
Forbidden Sanctuary  Bowker, Richard

Web of Everywhere  Brunner, John

The Stardroppers  Brunner, John
New Writings in SF-7  Carnell, John

Under the Green Star  Carter, Lin

The Dreamstone   Cherryh, C.J. *
Childhood’s End  Clarke, Arthur C.

 
Spock, Messiah!  Cogswell, Theodore R.

Duende Meadow  Cook, Paul *

 
The Cloud Walker  Cooper, Edmund

Sea-Horse in the Sky Cooper, Edmund

Transit  Cooper, Edmund

The Overman Culture  Cooper, Edmund

 
A.I.s    Dann, Jack *

 

The Alchemist’s Pursuit   Duncan, Dave

Swimmers Beneath the Bright  Easton, M. Coleman
Iskiir  Easton, M. Coleman

Star-Anchored, Star-Angered  Elgin, Suzette Haden

The Stone God Awakens  Farmer, Philip José

The Unreasoning Mask  Farmer, Philip José

By the Time I Get to Nashville  Fenn, Lionel
Cyber Way  Foster, Alan Dean

Copernick’s Rebellion  Frankowski, Leo

Plainsong: A Thomas Dunne Book  Grabien, Deborah

Vengeance For A Lonely Man (Hawk & Fisher, #4)  Green, Simon R.

The Silver Bear (Silver Bear, #1)  Haas, Derek

The Mind Brothers  Heath, Peter

The Sleep Eaters  Lymington, John

The Seekers of Shar-Nuhn  Mayhar, Ardath

The Forgotten Beasts of Eld  McKillip, Patricia A.

A Place Beyond Man: The Archives of Varok  Neeper, Cary

Virtual Zen  Nelson, Ray Faraday
Protector (Known Space)  Niven, Larry

The Crystal Gryphon (Witch World Series 2: High Hallack Cycle, #5)  Norton, Andre

A Plague of Pythons  Pohl, Frederik
The Cool War  Pohl, Frederik

Stepfather Bank  Poyer, David

The Tears of the Singers  Snodgrass, Melinda M.

The People Beyond the Wall   Tall, Stephen