Interesting. I’ve read most of the books mentioned by everyone so far in this thread, but there are thirteen authors’ names I’m unfamiliar with. (In the interest of full disclosure, those names are Asher, Boulle, Carsac, Cisco, MacLeod, Matheson, Rassel, Reynolds, Robson, Strutgatsky, Sullivan, Jeffrey Thomas, and Wright.)
A few of the authors named in this thread don’t fire my jets, but the vast majority of the authors and titles would appear on my own list of suggested reading. Here, I’ll try not to repeat titles mentioned by others, except for a few books that I truly love and the four books I’ve listed as essential reading.
The list below is organized into sections so that you can scan the bold-font headings for areas of personal interest. (OK, the headings are highly subjective, but what the heck.) The entire list is skewed toward soft rather than hard science fiction.
Four essentials
Frank Herbert, Dune
Ursula K. Le Guin, Left Hand of Darkness
Philip K. Dick, Man in the High Castle
Ray Bradbury, The Martian Chronicles
Religion
Mary Doria Russell, The Sparrow
Robert Sawyer, Calculating God
Fantasy (SF with strong fantasy elements)
Pat Murphy, The City Not Long After
Michaela Roessner, Vanishing Point
Joan D. Vinge, The Snow Queen
Steven Gould, Helm
Tolkien
Pat Murphy, There and Back Again
World-building
Kim Stanley Robinson, Red Mars
John Varley, Steel Beach
Vernor Vinge, A Fire Upon the Deep and A Deepness in the Sky
Sheri Tepper, Grass
Philosophy
Philip K. Dick, Do Androids Dream of Electric Sheep?
Gene Wolfe, The Fifth Head of Cerberus
Love and lust
Anne McCaffrey, Restoree
Catharine Asaro, the Skolian Empire books
S.L. Viehl, Stardoc
Karin Lowachee, Warchild
Tanith Lee, Silver Metal Lover
Lois McMaster Bujold, the Miles Vorkosigan books
Sharon Lee and Steve Miller, the Liaden books
George Nader, Chrome
Plucky males coming of age
Charles Sheffield and Jerry Pournelle, Higher Education
Steven Gould, Jumper
Fans reviving a space program
John Varley, Red Thunder
Larry Niven, Jerry Pournelle, and Michael Flynn, Fallen Angels
Ecology
John Brunner, Stand on Zanzibar
Disabilities and mortality
Elizabeth Moon, The Speed of Dark
James Alan Gardner, Expendable
Connie Willis, Passages
Post-apocalyptic fiction
David Brin, The Postman
George R. Stewart, Earth Abides
Octavia Butler, Parable of the Sower
African-American history
Octavia Butler, Kindred
Steven Barnes, Lion’s Blood
Native Americans
Kage Baker, Sky Coyote
Pamela Sargent, Climb the Wind
Humor and English history
Connie Willis, To Say Nothing of the Dog
Theater
John Varley, The Golden Globe
Experimental fiction
Samuel Delaney, Dhalgren
Quirky imagination
Cordwainer Smith, Norstrilia
Howard Waldrop, Howard Who? (collection)
Women with guns
Elizabeth Bear, Hammered
Aliens
Julie E. Czerneda, Thousand Words for Stranger and Survival
C.S. Friedman, The Madness Season
C.J. Cherryh, Cuckoo’s Egg
Octavia Butler, Dawn
Karen Traviss, City of Pearl
Shapeshifters
Julie E. Czerneda, Beholder’s Eye
Telepaths
Joan D. Vinge, Catspaw
Wolves
Wen Spencer, Alien Taste
Ambiguous gender punk
Emma Bull, Bone Dance
Feminism
Pamela Sargent, The Shore of Women
Margaret Atwood, The Handmaid’s Tale
Torture
Elizabeth Lynn, The Sardonnyx Net
C.J. Cherryh, Cyteen
Distrubingly dark villains
M.J. Engh, Arslan