"Diaspora" by Greg Egan has a great story, huge ideas, and probably the most cogent explanation of sentience/sapience ever written.
"The Diamond Age, or A Young Lady's Illustrated Primer" and "Accelerando" have already been mentioned.
"Reteif!" Made me laugh out loud. Larry Niven's "Destiny's Road" points out the difficulty of interstellar colonization. "Ringworld" blew my mind. Gene Wolfe's "The Book of the New Syn" taught me to pay attention; "Dirk Gently's Holistic Detective Agency" by Douglas Adams reinforced the lesson.
There are a lot of good ones; I could go on for ages...
https://en.wikipedia.org/wiki/A_Deepness_in_the_Sky
It's easy to categorise these as wonderful and well written space opera, but that undersells them. Their author (Venor Vinge) invented the idea of the Singularity, and worked as a computer science professor. Both won both the Hugo Award.
https://en.wikipedia.org/wiki/Ender's_Game
As good as people say it is.
Most of Richard Morgan's works (esp the https://en.wikipedia.org/wiki/Takeshi_Kovacs series). Not his fantasy books though.
For fantasy books, Patrick Rothfuss is doing good stuff. The Kingkiller Chronicles is excellent. Read his other books before "Slow Regard of Silent Things", though, because that is one weird story.
From more recent SciFi books:
https://en.wikipedia.org/wiki/The_Windup_Girl is excellent.
I'm currently reading Ancillary Justice and I'm really enjoying it. https://en.wikipedia.org/wiki/Ancillary_Justice
This is seriously impressive considering that it was published in 1998. My current hypothesis is that he's a time traveller messing with us.
"Heavy Weather" is probably the book of his that's most similar to Distraction - also very very good.
Accelerando (Charlie Stross) - truly epic, hard-scifi, from near to far future, truly hardcore
Diamond Age (Neal Stephenson) - awesome tale, plenty of nanotech, almost fairy-tale-esque
[Edit: formatting]
I still love Gibson, even his later books.
I want to say one of my favourite books is "Salt" by Adam Roberts. I love the characters and description of political views and the way the war between factions plays out. Roberts' other books are pretty good too.
I loved REAMDE - I could have done with a bit more inside the game and a bit less tramping through the woods. I love Stephenson's other books too.
Finally: Bruce Sterling seems to be under-appreciated. Hard to recommend one of his books.
This question is perhaps a FAQ. Has anyone on HN ever scraped the answers posted to the various threads, added information about number of mentions or votes; with links to Amazon (and other book sellers)?
Having some carefully chosen adds and duplicating all the links with affiliate links would turn this into a mostly passive income project.
Neuromancer - William Gibson
Nineteen Eighty-Four - George Orwell
Perdido Street Station - China Mieville
Snow Crash - Neal Stephenson
Ender's Game - Orson Scott Card
Foundation series - Asimov
among others...
"Chronicles of Amber" by Roger Zelazny - for imagination and badassery
Favorite short story is "Understand" by Ted Chiang - mind-expanding ;)
Also in general the lesser known Heinlein books are amazing. Not a fan of Stranger in a Strange Land. Named my current company after a reference to The Moon is a Harsh Mistress.
http://en.wikipedia.org/wiki/Stranger_in_a_Strange_Land
It's one of those books that just takes a while to digest after you are done reading it. I highly recommend it.
Every time I read a novel written by Dukaj I start feeling smarter. The ideas presented by characters are always worth considering and eye-opening.
Today, it's a bit less clear, but here is what comes to mind.
Rendezvous with Rama - Arthur C. Clarke
Worthing Saga - Orson Scott Card
EDIT: Come to think of it, I don't know is in the right category as Sci/fi. Well if not cryptonomicon, then SnowCrash probably :-P
The Left Hand of God Trilogy The Bad Company series Iain M Banks Sci-Fi Philip Jose Farmer Riverworld