Ender's Game is a terrific book written in the 20th century.

The Relic Keeper

removed Diaspora (which is a great book) because it was first published in 1997

altered carbon was a reajjy amazing book couldnt put it down

I'm very dubious about a lot of these books qualifying as hard SF. I get the Expanse novels, Himlton and Reynolds are popular and like a lot of those myself. While they might adhere to out scientific understanding more than you're average SF, they definitely don't focus on the science itself, as say your typical Watts, Egan or Baxter novel.

Jeroen wrote: "I'm very dubious about a lot of these books qualifying as hard SF. I get the Expanse novels, Himlton and Reynolds are popular and like a lot of those myself. While they might adhere to out scientif..."
I was terribly disappointed in the first Expanse book. It started out so well, with this great setup and the wonderful world-building. They also had interesting characters, and this brewing war between Earth and the Belters...and then it ended up being about vomit zombies. The characters did manage to make it bearable, but the plot was just so disappointing to me. I understand why Syfy picked it up though, they love producing stuff with more slime than substance, and I'm guessing the story suffered even more when they turned it into television.

Rosemary wrote: "altered carbon was a reajjy amazing book couldnt put it down"

Yep, it is fantastic

V.R. wrote: "Jeroen wrote: "I'm very dubious about a lot of these books qualifying as hard SF. I get the Expanse novels, Himlton and Reynolds are popular and like a lot of those myself. While they might adhere ..."

I think the Expanse series is more like a space opera rather than a hard sci-fi.

Can someone please remove Red Mars and Ringworld from the list? It is 20th century.

V.R. wrote: "Jeroen wrote: "I'm very dubious about a lot of these books qualifying as hard SF. I get the Expanse novels, Himlton and Reynolds are popular and like a lot of those myself. While they might adhere ..."

It's not *about* the vomit zombies; that's just the first noticeable stage of protomolecule infection as described by the blue-collar crew of the Rocinante when they encounter the situation on Eros. That scene is early in the series and does not occur again, and the protomolecule evolves from there (but the "vomit zombies" were their handhold into human evolution, which is necessary for the rest of its actions in the following books).

removed Old Man's War

Arthur C Clarke's The City and the Stars was published in 1956, according to its Goodreads page. I think somebody missed the '21st Century' bit in the title...

The Mote In God's Eye - (first published 1974)

Dune needs to be removed. 20th century.

Crystal wrote: "Dune needs to be removed. 20th century."

done

The Flying Sorcerers was originally published in 1974

V wrote: "The Flying Sorcerers was originally published in 1974"

deleted.

I'm also having some doubts about "hard sci-fi-ness" of some of these books...

Here's a list of books that need to be removed (I did not include two that were published in 1999 by noted hard-sf authors). Most of the below were first published in 20th century but some have other reasons that they need to be removed (e.g. duplicate listings). There are likely a number of other books that should be removed as well (e.g. not really hard-sf). But at least this is a start.

27. Use of Weapons (Iain M. Banks) (1990, 411 pp)
41. The Mote in God's Eye (Larry Niven) (1974, 560 pp)
60. A Fire Upon the Deep (Vernor Vinge) (1992, 631 pp)
66. Remembrance of Earth's Past trilogy (Cixin) (2017, 1545 pp) #NOTE: duplicate listing. Individual books at listed at #3, #9, #11
79. The Forever War (Joe Haldeman) (1974, 278 pp)
87. Friday (Robert A. Heinlein) (1982, 384 pp)
86. The Divinity Protocol (Berkeley Johnson) (2017, 320 pp) #NOTE: duplicate listing. Already at #84
91. Winter Eternal: Book I The River That Flows Two Ways (E. Thomas Joseph) (2017, 370 pp) # Historical fiction... not seeing it shelved as Hard-SF
91. Time and Time Again: Sixteen Stories of Time Travel (Robert Silverberg) (2018, 464 pp) # I'm gonna guess most of Silverberg's short stories were NOT written in the 21st century
91. Shatter (Annya Ginger) (2018, 193 pp) # M/M Sci-Fi Romance (not quite the "hard" we're looking for)
91. Red Mars (Kim Stanley Robinson) (1992, 572 pp)
101. The Children of Men (P.D. James) (1992, 241 pp)
101. Green Mars (Kim Stanley Robinson) (1993, 624 pp)
104. Foundation (Isaac Asimov) (1951, 244 pp)
104. Cat's Cradle (Kurt Vonnegut) (1963, 306 pp)
108. Firestar (Michael Flynn) (1996, 896 pp)
108. Fahrenheit 451 (Ray Bradbury) (1953, 175 pp)
111. The Martian Chronicles (Ray Bradbury) (1950, 182 pp)
112. The Running Man (Richard Bachman (Pseudonym), aka Stephen King) (1982, 317 pp)
113. V for Vendetta (Alan Moore) (1990, 296 pp)

Cydonical wrote: "Here's a list of books that need to be removed (I did not include two that were published in 1999 by noted hard-sf authors). Most of the below were first published in 20th century but some have oth..."

Thanks, cleaned up the list a bit.

There are still those I doubt count as 'hard sci-fi' but left them alone for now

Thanks, Loreley! I've reviewed the now current list and here are the remaining items that I think should be considered for either removal or re-thinking on the approach (sans the "is it hard sci-fi?" issue... I'll leave that one be). The biggest conundrum I have is the omnibus vs. individual books issue. Even though it would probably be best to have things as individual books, I'm OK (for now) having it either one way or the other per series... but I don't think any particular series should be listed BOTH ways. Here's the current culprits:

Cixin's "Remembrance of Earth's Past" series:
3. The Three-Body Problem (Liu Cixin) (2008, 400 pp) (Remembrance of Earth’s Past #1)
9. The Dark Forest (Liu Cixin) (2008, 512 pp) (Remembrance of Earth’s Past #2)
11. Death's End (Liu Cixin) (2010, 604 pp) (Remembrance of Earth’s Past #3)
63. Remembrance of Earth's Past trilogy (Cixin) (2017, 1545 pp)

So, since we have the individual books of Cixin's trilogy already listed as #3, #9, and #11... it is redundant to have the omnibus version listed at #63. I'm saying this since many books on this list are part of series and they are all listed individually as well (and not their omnibus counterparts).

And now, the exceptions (thus far) to that rule. Below we have two omnibus versions that do not have their individual books listed:

55. Void Box Set (Peter F. Hamilton) (2014, 2292 pp)
85. The Frontiers Saga: Episodes 1-3 (Ryk Brown) (2012, 657 pp)

So, maybe just leave these two that way until their individual books start popping into the list? This is where my conundrum lies... having a mixed standard is a recipe for future problems... but since the list isn't a mile long, perhaps we can still have it mixed until it becomes a bigger problem. Still, I think the list should have a series either one way or the other... not both. So, I'm still recommending the removal of #63.

Next issue, time period. I'm going to still recommend the removal of:

85. Time and Time Again: Sixteen Stories of Time Travel (Robert Silverberg) (2018, 464 pp)

Even though this compilation was published in 2018, here's the actual dates of the 16 individual stories:

1956 ABSOLUTELY INFLEXIBLE
1983 NEEDLE IN A TIMESTACK
1974 TRIPS
1973 MANY MANSIONS
1983 HOMEFARING
1972 WHAT WE LEARNED FROM THIS MORNING’S NEWSPAPER
1991 HUNTERS IN THE FOREST
1982 JENNIFER’S LOVER
1984 SAILING TO BYZANTIUM
1973 BRECKENRIDGE AND THE CONTINUUM
1982 THE MAN WHO FLOATED IN TIME
1982 GIANNI
1982 THE FAR SIDE OF THE BELL-SHAPED CURVE
1983 DANCERS IN THE TIME-FLUX
1967 HAWKSBILL STATION
2007 AGAINST THE CURRENT

So, only ONE short story is >=2000 publishing date. And this particular short story (Against the Current) is also published in the following compilation:

The Year's Best Science Fiction: Twenty-Fifth Annual Collection (2008, 652 pp, ISBN 9780312378608).

So, if you want to keep that ONE short story that is >=2000 publishing date and have it as part of a compilation book where the rest of the shorts stories in the books are also >=2000, then this would likely be a better option.

Only other issue is the two books that are really published in 1999. But since they are from notable hard-sf authors, I'm inclined to leave them (and they are both the beginning books of series that extend into >=2000 publishing time frame). I'll list them here just for reference but, again, I'm OK with leaving them in the list:

52. Manifold: Time (Stephen Baxter) (1999, 480 pp) (Manifold #1)
67. Starfish (Peter Watts) (1999, 384 pp) (Rifters #1)

So, I still think #63 and #85 should be removed... maybe add ISBN 9780312378608... and I'll leave you to brood over the #52, #67 omnibus issue.

Sorry to be a pest... just trying to help. And the list really is looking a lot better. Thanks again for maintaining it! And here's hoping it can really serve it's purpose well in the years to come :)