Wooz said:
Philip K. Dick. Dr.Bloodmoney
Postnuclear California. One of the best Sci-Fi books I ever read, and definitely the best post-apoc setting EVAR.
Owned it, love it, and generally agree. (Incidentally, I also fit all three of the criteria listed above by TVD.) Thought the ending was kind of disjointed, though.
On the subject of hard sci-fi, Overseer, I don't suppose there's any chance that you
haven't read Carl Sagan's
Contact, but if not, it fits most of the criteria you've put out. The story follows a scientist through her early career and into project leadership at SETI, where they intercept and painstakingly decode a signal that seems to be proof of extraterrestrial intelligence. It gets deeper than that, but the nature and pacing of the story are such that revealing anything else would spoil the lion's share of the book. I
would be comfortable telling you that it incorporates mathematics, logic, space, acadamia, the biases and cults of personality inherent in scientific circles, the possibility of extraterrestrials, and the question of an "ultimate intelligence." Though it resembles 'soft' sci-fi in the focus it gives to the main character's life and thoughts, it definitely satisfies the "Hey, look! Science!" requirement missing in much of modern soft, and even hard, science fiction. Suffice it to say, it
does make you think.
The story isn't completely free of romantic elements, but if memory serves, they either 1.)integrated naturally, or 2.) weren't given too much center-stage attention, or 3.)both.
As far as Orson Scott Card goes,
Ender's Game is fine and dandy, but I'd go for the littler-know
Pastwatch: The Redemption of Christopher Columbus.