
Dracula
Bram Stoker
4.5 on Amazon
13 HN comments

Red Rising
Pierce Brown, Tim Gerard Reynolds, et al.
4.6 on Amazon
13 HN comments

The Secret
, Ted Mann, et al.
4.5 on Amazon
12 HN comments

The Time Traveler's Wife
Audrey Niffenegger, Fred Berman, et al.
4.4 on Amazon
9 HN comments

I, Robot
Isaac Asimov, Scott Brick, et al.
4.5 on Amazon
9 HN comments

Heretics of Dune: Dune Chronicles, Book 5
Frank Herbert, Simon Vance, et al.
4.7 on Amazon
9 HN comments

Neverwhere
Neil Gaiman and HarperAudio
4.6 on Amazon
8 HN comments

Mr. Penumbra's 24-Hour Bookstore
Robin Sloan
4.2 on Amazon
8 HN comments

Metro 2033
Dmitry Glukhovsky, Rupert Degas, et al.
4.7 on Amazon
8 HN comments

The Light Fantastic: A Novel of Discworld
Terry Pratchett
4.7 on Amazon
7 HN comments

The Wise Man's Fear: Kingkiller Chronicle, Book 2
Patrick Rothfuss, Nick Podehl, et al.
4.7 on Amazon
7 HN comments

Welcome to the Monkey House: A Collection of Short Works
Kurt Vonnegut Jr.
4.7 on Amazon
7 HN comments

Stardust
Neil Gaiman and HarperAudio
4.6 on Amazon
7 HN comments

Warbreaker
Brandon Sanderson, Alyssa Bresnahan, et al.
4.7 on Amazon
7 HN comments

The Ocean at the End of the Lane: A Novel
Neil Gaiman and HarperAudio
4.5 on Amazon
7 HN comments
wrsh07onJuly 8, 2015
coder-3onMay 25, 2021
impalallamaonDec 14, 2020
sp332onMar 21, 2014
petervidanionSep 12, 2008
andrewlonMar 22, 2008
Star Trek, the original series
I, Robot by Isaac Asimov. The first science fiction story I read, which lead to all the others.
The Annotated Alice by Lewis Carroll and Martin Gardner. That's Alice's Adventures in Wonderland and Through the Looking Glass, by Lewis Carroll, with wonderful annotations by Martin Gardner.
AnIdiotOnTheNetonJuly 8, 2018
One of Asimov's I, Robot stories did a similar thing, with a robot on a space station making rational arguments against the existence of earth.
Of course, there are also nutters...
Wiles_7onApr 11, 2018
https://en.wikipedia.org/wiki/I,_Robot_(short_story)
AnIdiotOnTheNetonJuly 23, 2021
Anything by Greg Egan is probably going to be the hardest sci-fi you've ever read. Dude wrote a book where he considered the ramifications of a universe built on a positive-definite Riemannian metric, and another one where the universe has 2 time dimensions.
Robert L. Forward's Dragon's Egg explores what life might look like if it evolved on a neutron star.
Adrian Tchaikovsky's Children of Time and Children of Ruin explore the evolution of other earth species if they were given a kick towards sapience.
Vernor Vinge's A Fire Upon the Deep is half space adventure (not very hard) and half an exploration of a lifeform which only achieves sapience in small groups. A Deepness in the Sky is generally harder and explores a lot of things, including the power of focused human attention, the difficulty of galactic scale civilization, and alien life evolved in a star system where the star periodically dims.
Steven Baxter and Clarke collaborated on The Light of Other Days, which explores the technical and sociological consequences of a device which allows you to see the past.
With a broad interpretation of 'hard' I can highly recommend Ursula Le Guin's The Left Hand of Darkness and The Dispossessed, which have soft science but hard humanity.
Similarly The Long Earth series, a collaboration between Pratchett and Baxter, where it seems Baxter handles the sociological and technological consequences of the science while Pratchett handles the characters and philosophy.
Asimov's I, Robot is an exploration of what happens when you try to constrain intelligence with rules.
Asimov's Foundation Trilogy gets a lot of hype, but it isn't very hard and I also found it utterly mediocre. Instead I recommend The God's Themselves, which is so good it's like Asimov was channeling a much better writer to get his ideas down. It explores the limited interaction of our universe with one that has slightly different physical properties.
Also perhaps stretching the definition of 'hard', but I want to recommend it because it's relatively unknown, is Leonard Richardson's Constellation Games, in which an incredibly advanced multi-species anarchic alien civilization makes first contact with humanity, and the protagonist really just wants to play their video games. It's actually harder sci-fi than it sounds.