Dune by Frank Herbert
Flowers for Algernon by Daniel Keyes and Babel-17 by Samuel R Delany (tie)
The Einstein Intersection by Samuel R Delany
Rite of Passage by Alexei Panshin
The Left Hand of Darkness by Ursula K Le Guin
Ringworld by Larry Niven
A Time of Changes by Robert Silverberg
The Gods Themselves by Isaac Asimov
Rendezvous with Rama by Arthur C Clarke
The Dispossessed by Ursula K Le Guin
The Forever War by Joe Haldeman
Man Plus by Frederik Pohl
Gateway by Frederik Pohl
Dreamsnake by Vonda N McIntyre
The Fountains of Paradise by Arthur C Clarke
Timescape by Gregory Benford
The Claw of the Conciliator by Gene Wolfe
No Enemy But Time by Michael Bishop
Startide Rising by David Brin
Neuromancer by William Gibson
Ender’s Game by Orson Scott Card
Speaker for the Dead by Orson Scott Card
The Falling Woman by Pat Murphy
Falling Free by Lois McMaster Bujold
The Healer’s War by Elizabeth Ann Scarborough
Tehanu: The Last Book of Earthsea by Ursula K Le Guin
Stations of the Tide by Michael Swanwick
Doomsday Book by Connie Willis
Red Mars by Kim Stanley Robinson
Moving Mars by Greg Bear
The Terminal Experiment by Robert J Sawyer
Slow River by Nicola Griffith
The Moon and the Sun by Vonda N McIntyre
Forever Peace by Joe Haldeman
Parable of the Talents by Octavia Butler
Darwin’s Radio by Greg Bear
Quantum Rose by Catherine Asaro
American Gods by Neil Gaiman
The Speed of Dark by Elizabeth Moon

30 out of 40. Need to reread No Enemy But Time though as I can’t remember much about it.