When I started writing in the early Nineties horror and fantasy took over my reading preferences, but I once read an awful lot of SF. Here’s twenty novels I remember fondly.
Nova – Samuel Delaney
Lord of Light – Roger Zelazny
The Chrysalids – John Wyndham
Stand on Zanzibar – John Brunner
More than Human – Theodore Sturgeon
Up the Walls of the World – James Tiptree, Jr (Alice Sheldon)
The Forever War – Joe Haldeman
The Left Hand of Darkness – Ursula Le Guin
Rendezvous With Rama – Arthur C Clarke
Neuromancer – William Gibson
Where Late the Sweet Birds Sang – Kate Wilhelm
A Canticle for Leibowitz – Walter M Miller Jr.
The Drowned World – J G Ballard
Tau Zero – Poul Anderson
The Man in the High Castle – Philip K. Dick
Cat’s Cradle – Kurt Vonnegut
Rite of Passage – Alexei Panshin
Downbelow Station – C.J. Cherryh
Rogue Moon – Algis Budrys
The Island of Dr. Moreau – H G Wells.
"Rim" by Alexander Besher is a pretty good VR novel though the ending's kind of a deus ex machina in a way, but a lot of the rest of the book really puts you on the edge of your seat. (An old friend of mine told me Besher did a sequel called "Mir" but I still have to pick that one up to see what it's like.)
Hope I could add some good suggestions to your list. :)